SEO in plain English: 47 terms, defined

SEO has a vocabulary problem. Most glossaries define each term using three other terms you haven't met yet, so you finish the entry knowing less than when you started.

These are the terms you'll actually encounter in your first few months, grouped by the part of the process they belong to. Read it top to bottom the first time; each group builds on the one before it.

How Google finds your pages

• Crawler (or bot, or spider) — a program Google runs that visits web pages and follows the links on them. Googlebot is the one that matters.
• Crawling — the act of visiting your pages. A page can be crawled and still never appear in search results.
• Indexing — Google deciding to store your page and consider showing it to searchers. This is the step that actually matters.
• The index — Google's stored copy of the web. If your page isn't in it, no amount of optimisation will help.
• Sitemap — a file listing your pages, usually at yourdomain.com/sitemap.xml, that tells Google what exists without making it hunt.
• robots.txt — a file at the root of your site telling crawlers where they may and may not go. A stray "Disallow: /" line hides your entire site.
• noindex — a tag on a page telling Google not to store it. Useful for thank-you pages, catastrophic when left on by accident.
• Canonical tag — a note saying "this page and that page are the same, count that one". It stops near-identical URLs from competing with each other.
• Redirect — sending visitors and Google from an old URL to a new one. A 301 means permanent, which is the one you almost always want.

Searching and ranking

• Query — what someone actually typed into the search box.
• Keyword — the phrase you're hoping to be found for. The same thing as a query, seen from your side of the transaction.
• Long-tail keyword — a longer, more specific phrase. Fewer people search "crm for wedding photographers" than "crm", and the ones who do are much easier to win and much more likely to buy.
• SERP — the search engine results page. Everything Google shows for a query, not just the ten blue links.
• Position (or ranking) — where your page sits in that list. Position 1 is the top non-ad result.
• Impression — your page appeared in someone's results, whether or not they noticed it.
• Click-through rate (CTR) — the share of impressions that turned into clicks. Low CTR at a good position usually means your title isn't matching what people wanted.
• Featured snippet — the answer box Google sometimes puts above the results, pulled from a page. It gets clicks, and it can also answer the question so completely that nobody clicks.
• SERP feature — anything on a results page that isn't a standard result: maps, images, People Also Ask, shopping carousels.

What's on the page

• Title tag — the clickable headline in search results. Different from the headline on the page itself, and often the most useful thing you can rewrite.
• Meta description — the grey summary under the title. It doesn't affect ranking directly; it affects whether anyone clicks.
• H1 — the main visible heading on the page. One per page.
• H2, H3 — subheadings, in descending order of importance. They give the page a structure both readers and Google can follow.
• Slug — the readable part of a URL after the domain. In /blog/seo-glossary, the slug is seo-glossary.
• Alt text — a written description of an image, read aloud by screen readers and used by Google to understand the picture.
• Internal link — a link from one page of your site to another. The cheapest ranking improvement available to you, and the most neglected.
• Anchor text — the visible words of a link. "Our pricing page" tells Google more than "click here" does.
• Structured data (or schema) — code in the background describing what a page is, which can earn you star ratings, FAQs or recipe cards in results.

Links from other sites

• Backlink — a link from someone else's site to yours. Still one of the strongest signals Google uses.
• Referring domain — a unique site linking to you. Ten links from one blog count for far less than one link each from ten blogs.
• nofollow — an attribute telling Google not to pass credit through a link. Most social media and comment links carry it.
• Domain authority — a score invented by SEO tools, not by Google, estimating how strong a site is. Useful for rough comparison, not a number Google sees.
• Link building — the work of getting other sites to link to you. Also the part of SEO most likely to get you into trouble if you buy your way through it.
• Toxic links — spam links pointing at your site, usually not your doing. Almost always safe to ignore.

How content gets judged

• Search intent — what the searcher actually wanted. Someone typing "running shoes" wants to shop; "how to clean running shoes" wants instructions. Matching intent matters more than matching words.
• Topical authority — Google's sense that your site is a serious source on a particular subject, built by covering it thoroughly rather than glancingly.
• Content cluster — a group of articles on one subject, linked to each other.
• Pillar page — the broad, thorough article at the centre of a cluster that the others link back to.
• Thin content — a page without enough substance to be worth storing. Usually short, generic, or assembled from other pages.
• Keyword cannibalisation — two of your own pages competing for the same search, so neither ranks well. The fix is usually to merge them.
• Content decay — the slow slide of an old article down the rankings as it goes out of date. Fixed by updating rather than replacing.

Measuring what happened

• Organic traffic — visitors who arrived from unpaid search results, as opposed to ads, social, or email.
• Session — one visit. A person who comes back tomorrow counts as two sessions and one visitor.
• Bounce rate — the share of visits where someone left without a second action. Genuinely high for blog articles, which isn't automatically bad; a reader can get their answer and leave happy.
• Conversion — the action you actually wanted: a signup, a sale, a booking, a form.
• Attribution — deciding which article gets credit when someone reads three of them before converting.
• First-touch — crediting the article that brought a person to your site for the very first time.
• Last-touch — crediting the article they read immediately before converting. Both are worth reporting; they answer different questions.

If you keep only two things from this list, keep the difference between indexing and ranking, and the difference between impressions and clicks. Most confusion about why a site isn't working comes down to conflating one of those pairs.