SEO Acronyms: The Abbreviations That Matter, Grouped by What They Do

SEO runs on abbreviations, and most glossaries list them alphabetically, which is the least useful order when you are trying to understand how they relate. This one groups them by what they are for.

Two sections at the end cover the parts that cause real confusion: acronyms whose meaning has changed, and pairs that get used interchangeably when they mean different things.

Rankings and results pages

• SERP. Search engine results page. The page returned for a query, covered in full in our guide to SERP meaning.
• SEO. Search engine optimisation. Earning visibility in unpaid search results.
• PAA. People Also Ask. The expandable question box on a results page. Google’s own documentation calls this the related questions group.
• FS. Featured snippet. An answer pulled onto the results page from a ranking page.
• AIO. AI Overview. Google’s AI generated answer block at the top of some results.
• KP. Knowledge Panel. The information box about an entity, usually on the right on desktop.
• LP. Local pack. The map plus three business listings shown for local intent queries.
• SGE. Search Generative Experience. The experimental name Google used before AI Overviews.
• ZCS. Zero click search. A search that ends without a click through to any website.
• GEO. Generative engine optimisation. Optimising to be cited in AI generated answers.
• AEO. Answer engine optimisation. Much the same idea, used by different people.
• SEM. Search engine marketing. Usually means paid search, though some use it to cover paid and organic together.

Metrics and measurement

• CTR. Click-through rate. Clicks divided by impressions.
• CVR. Conversion rate. Conversions divided by visits or sessions.
• CRO. Conversion rate optimisation. Improving the share of visitors who convert, explained in our piece on how CRO works.
• KPI. Key performance indicator. The measures a project is judged on.
• ROI. Return on investment. Gain relative to cost.
• GSC. Google Search Console. Google’s free reporting for how your site performs in search.
• GA4. Google Analytics 4. The current version of Google Analytics.
• GTM. Google Tag Manager. A container for managing tracking tags without editing site code.
• MoM and YoY. Month on month and year on year. Comparison windows, and the second is the honest one for seasonal sites.
• SOV. Share of voice. Your visibility across a keyword set relative to competitors.
• CPC. Cost per click. A paid metric, often used in SEO tools as a proxy for commercial value.
• RPM. Revenue per mille. Earnings per thousand pageviews, common in publisher reporting.

Core Web Vitals and page performance

• CWV. Core Web Vitals. Google’s set of user experience measurements.
• LCP. Largest Contentful Paint. Loading speed, good at 2.5 seconds or less. Source: web.dev.
• INP. Interaction to Next Paint. Responsiveness, good at 200 milliseconds or less.
• CLS. Cumulative Layout Shift. Visual stability, good at 0.1 or less.
• FID. First Input Delay. The responsiveness metric INP replaced in 2024.
• TTFB. Time to First Byte. How long the server takes to start responding.
• FCP. First Contentful Paint. When the first content appears on screen.
• CrUX. Chrome User Experience Report. Google’s dataset of real Chrome user measurements.
• RUM. Real user monitoring. Performance measured from actual visitors rather than a lab test.
• CDN. Content delivery network. Distributed servers that shorten the distance to your visitors.

Links and authority

• DA. Domain Authority. Moz’s score predicting ranking strength, on a 1 to 100 scale.
• DR. Domain Rating. Ahrefs’ equivalent, based on backlink profile strength.
• PA. Page Authority. Moz’s per page version of DA.
• UR. URL Rating. Ahrefs’ per page version of DR.
• AS. Authority Score. Semrush’s domain strength metric.
• TF and CF. Trust Flow and Citation Flow. Majestic’s two link metrics, quality and quantity respectively.
• RD. Referring domains. The count of distinct sites linking to you, which matters far more than raw link count.
• PR. PageRank. Google’s original link algorithm. The public toolbar score was retired years ago, so any tool offering you a PageRank number today is showing its own estimate.
• NoFollow, UGC and Sponsored. Link rel attribute values, the last two for user generated content and paid or sponsored links. Covered in do nofollow links help SEO.
• Web 2.0. Not an acronym, but used as shorthand for free hosted platforms used in link building.

Technical SEO

• XML. Extensible Markup Language. The format sitemaps use.
• HTML. HyperText Markup Language. The markup search engines parse.
• CSS and JS. Cascading Style Sheets and JavaScript. Presentation and behaviour, both of which affect what a crawler sees.
• SSR and CSR. Server side rendering and client side rendering. The first gives crawlers finished HTML, the second asks them to run JavaScript first.
• URL. Uniform Resource Locator. A page address.
• HTTPS. The encrypted version of HTTP.
• SSL and TLS. The certificate technology behind HTTPS. SSL is the older name still in common use.
• 301 and 302. Permanent and temporary redirects.
• 404 and 410. Not found and permanently gone.
• 5xx. Server error responses, the ones that cost you crawl budget fastest.
• Hreflang. The attribute declaring language and regional targeting.
• AMP. Accelerated Mobile Pages. A stripped down page format, far less relevant than it once was.
• CMS. Content management system, such as WordPress.
• API. Application programming interface. How tools pull data programmatically.

Content and search quality

• E-E-A-T. Experience, Expertise, Authoritativeness and Trustworthiness. The extra E for Experience was added in December 2022 as part of Google’s quality rater guidelines. Source: Google Search Central.
• YMYL. Your Money or Your Life. Topics where poor information could cause real harm, held to a higher quality bar.
• QRG. Quality Rater Guidelines. The document Google’s human raters work from.
• NLP. Natural language processing. How search engines parse meaning in text.
• LLM. Large language model. The technology behind AI answers and AI writing tools.
• TF-IDF. Term frequency, inverse document frequency. An old weighting measure for how distinctive a term is in a document.
• LSI. Latent semantic indexing. Widely repeated in SEO content and not something Google has said it uses.
• UX. User experience.
• CTA. Call to action.
• TOC. Table of contents.

Tools and platforms

• KWR. Keyword research.
• KD. Keyword Difficulty. A tool’s estimate of ranking difficulty. Each tool calculates it differently, so a KD from one is not comparable with a KD from another.
• MSV. Monthly search volume.
• GKP. Google Keyword Planner. A Google Ads tool whose forecasts cover paid search, not organic traffic.
• SF. Screaming Frog. A desktop crawler, compared in our Screaming Frog alternatives guide.
• GBP. Google Business Profile, formerly Google My Business.
• GMB. Google My Business. The old name for GBP, still used constantly.
• NAP. Name, address, phone. The business details that need to match across local listings.
• SaaS. Software as a service.
• SOP. Standard operating procedure.

Paid and adjacent marketing

• PPC. Pay per click. The pricing model for most search ads.
• CPM. Cost per mille, meaning cost per thousand impressions.
• CPA. Cost per acquisition.
• ROAS. Return on ad spend.
• SMM. Social media marketing.
• B2B and B2C. Business to business and business to consumer.
• UTM. The tracking parameters added to URLs to attribute traffic in analytics.
• AOV. Average order value.
• LTV. Lifetime value of a customer.

Acronyms whose meaning has changed

These are the ones that make older articles misleading, because the term still appears everywhere while the thing behind it moved.

• FID became INP. Interaction to Next Paint replaced First Input Delay as a Core Web Vital in 2024. Any guide still giving you FID targets is describing a metric Google no longer uses. Source: web.dev.
• E-A-T became E-E-A-T. The Experience E arrived in December 2022, so advice written before then is missing a quarter of the framework.
• SGE became AI Overviews. Same feature, renamed as it moved out of experiment.
• GMB became GBP. Google My Business was renamed Google Business Profile, though the old name is still in everyday use.
• PR stopped being public. Google retired the public PageRank score, so a PageRank figure in a tool today is that vendor’s own model.

Pairs that get mixed up

• DA and DR are not the same number. DA is Moz’s, DR is Ahrefs’. Neither is a Google metric, neither affects rankings directly, and comparing a DA from one report with a DR from another tells you nothing.
• KD from different tools is not comparable. Each vendor models difficulty its own way. Treat it as one tool’s opinion rather than a universal score.
• CTR and CVR. Click-through rate is about getting the click, conversion rate is about what happens after. Improving one can easily worsen the other.
• SEM and PPC. PPC is a pricing model, SEM is a channel. Not every SEM ad is priced per click.
• SEO, GEO and AEO. The second two describe optimising for AI generated answers, and they are largely the same idea with different labels rather than three distinct disciplines.
• CPM and RPM. Both are per thousand, but CPM is what an advertiser pays and RPM is what a publisher earns.

Frequently asked questions

What does SEO stand for?

SEO stands for search engine optimisation. It covers the work of earning visibility in unpaid search results, as opposed to paid advertising. The related term SEM usually means paid search, although some people use it to cover paid and organic together, which is a common source of confusion.

What is the difference between DA and DR?

DA is Domain Authority, a Moz score, and DR is Domain Rating, an Ahrefs score. Both estimate how strong a domain is, but they use different models and different scales, so the two numbers are not interchangeable. Neither is a Google metric and neither is used directly in ranking.

What does E-E-A-T stand for?

E-E-A-T stands for Experience, Expertise, Authoritativeness and Trustworthiness, and it comes from Google’s quality rater guidelines. The first E, for Experience, was added in December 2022, which is why older articles refer to E-A-T with three letters. It describes what human raters assess, not a direct ranking score.

Is FID still a Core Web Vital?

No. Interaction to Next Paint, or INP, replaced First Input Delay as a Core Web Vital in 2024. The current three are LCP for loading, INP for responsiveness and CLS for visual stability. Any guide still giving FID thresholds is describing a metric Google has retired.

What is the difference between GEO and SEO?

SEO is optimising to rank in search results, while GEO, meaning generative engine optimisation, is optimising to be cited in AI generated answers. AEO, or answer engine optimisation, describes much the same goal under a different label. In practice they overlap heavily rather than being separate disciplines.

Why do keyword difficulty scores differ between tools?

Each vendor builds its own difficulty model from its own index and its own weighting, so the same keyword can return very different scores. Treat KD as one tool’s opinion on relative difficulty rather than an absolute measure. Checking the actual results page is more reliable than trusting any single score.