SEO Glossary: The Basic Terms

I wrote this post in Spanish in 2021 and adapted it to English in 2026.

Before you even start learning SEO, you need to get familiar with the terms used most often in this little world.

Most people order this kind of SEO glossary alphabetically. I'll order it by what I think matters most to know, so by the time you're halfway down the list you may already know enough to follow any SEO talk.

Let's start with the most used terms and work down to the ones I consider just as basic, but that don't come up as often:

Keyword #

"Keywords" are the searches people make on Google. A rookie mistake is thinking every word is a keyword, but no. A single keyword can be a group of words, for example "how to raise a dachshund": those 5 words together form a single keyword.

Seed Keyword #

This is the keyword all the other keywords you'll go after in a niche derive from. For example, "coffee maker" is the seed keyword of a coffee maker niche, and from it you get "dolce gusto coffee makers", "drip coffee makers", and so on.

Long Tail #

Long-tail keywords (sometimes just "longtail") are keywords made up of a large number of characters (40 or more). They tend to be very specific, have low search volume and are usually pretty easy to rank for.

Domain #

The domain is the main URL all your content hangs from. It's the web address browsers use to show your website to the public.

TLD #

TLD stands for top-level domain, and it's the suffix your domain ends with (what comes after the dot). The most common is .com, and there are geo-targeted ones for each country, ones for professions like .lawyer, and many more.

Hosting #

Hosting, or a server, is a sort of "home" for your website. Think of it as a hard drive in the cloud that your visitors can reach to see the content you created for them.

Keyword Research #

This means searching for keywords: researching keywords so you can map out, categorize, rank and give structure to the content before building the website. More in my keyword research guide.

Keyword Mapping #

It's done after keyword research, or rather, it's one of its parts. In this phase you create a mind map with all the keywords you found during keyword research, to see how they connect to each other and how you could organize the categories.

Keyword Clustering #

This means grouping keywords by semantic affinity, search intent and/or hierarchy. It's done both for a website's content as a whole and for each piece of content you're going to create. More in my keyword clustering post.

Crawling #

It's the act of "climbing" through the "branches" of your website. Crawling is done by the robots of the different search engines, and it's the process through which the "spiders" discover each of the URLs that make up your website.

URL #

A URL is a child address of your website's main address. In other words, it's a subdirectory inside your domain (think of it as a subfolder inside the folder that is your domain on a hosting account, although it gets a bit more complicated when you use a CMS like WordPress, but we'll get to that later).

Crawl Budget #

It's the time a spider spends crawling your website. It's usually milliseconds, and the more optimized your website is, the less crawl budget a spider needs to discover all the URLs that make it up.

URL Architecture #

URL architecture is how you present your page URLs: whether you include the date or not, among other values you can add to each URL depending on what suits you or what you want it to do. More in my silo URL architecture post.

Interlinking #

Interlinking is how the URLs on your website talk to each other. In other words, a connection architecture (think of pipes or cables in a sewer or power network) between all the URLs that make up your website.

Backlinks #

Also just called "links", these are hyperlinks on other websites that point to your domain.

DR, Domain Authority or Just Authority #

It refers to how relevant a domain is to Google and other search engines. It's measured from 0 to 100, the closer to 100 the more relevant the domain, and it's directly related to the number of links the website gets.

UR, URL Authority #

It's the same as DR or domain authority, but applied to a single URL on your website. It's normal for the homepage URL to have the highest UR on your site, but there are cases where a URL (other than the homepage) ends up getting more links than the homepage, so it has the highest UR on the whole site.

Link Juice #

Link juice is a "measure" of how much strength is being passed to a given URL, and it depends on how many links that URL is getting. It's usually used to prioritize interlinking toward key pages (sending more internal/external links to those pages increases their link juice).

External Links #

Also called outbound links, these are links that point to addresses outside your domain. They can be follow or nofollow, and the difference is that one passes authority and the other doesn't. In other words, these are the backlinks you create for other websites.

Tags #

This is a whole world inside the world of SEO, because lots of things get called "tags". So I'll talk about them with a "last name", so you learn to tell them apart. Over time, the context in which the word "tag" is used will tell you what kind of tag people mean:

Meta tags

These are tags the user can't see but that are part of your website's code. They're used so search engines understand the structure of the content you've created. They include:

• HTML markup tags: tags that tell the browser how your content is laid out (body, header, h1, h2, img, among others).
• Structured data meta tags: these tags provide extra data, like the featured image, Schema markup, Open Graph, etc.
• SEO meta tags: these tags tell the browser your page's title and description, and you can customize them for each URL.

WordPress tags

These tags are a kind of taxonomy WordPress gives you as a tool to better organize the content on your website.

Social media tags

Although there's no way, for now, to use them on your website, I think they're worth mentioning, because it's a common mistake to start tagging a WordPress post as if it were a tweet. These tags (hashtags) only make sense on social networks, so don't confuse them with WordPress tags or code tags.