Essential SEO Terms for Beginners: What Are PBN, Ref Domains, and Sitewide Links?

If you only hear the terms but don’t really understand the concepts, it’s easy to get lost in conversations and have no idea what the real risks are in practice.

This article uses simple examples to explain a few common SEO terms:

• PBN

• Backlink

• Ref / Referring Domains

• Sitewide Links

1. What Is a Backlink?

Backlink = A link from another website pointing to your website.

For example:

• A blogger writes a post called “Best Dentists in Kaohsiung,” mentions your clinic, and adds a link to your website.

• For you, that is a backlink.

Why is it important?

In SEO, you can think of a backlink as a vote.
The more websites that link to you, the more people are “voting” for you.

However:

• More is not always better. You also need to look at:

  • Whether the linking site is trustworthy and has real content

  • Whether the topic is relevant (a dental clinic being massively linked from gambling sites is suspicious)

  • Whether the anchor text looks natural (clinic name, brand name, or URL-type anchors tend to be natural)

2. What Are Ref / Referring Domains?

When we look at backlinks, aside from the total number of links, there’s another important metric: Referring Domains (often shortened to Ref or RD).

Definition:

Referring Domains = How many different websites have linked to you.

Example:

• aaa.com links to you 50 times

• bbb.com links to you 10 times

• ccc.com links to you 2 times

Then:

• Backlinks (total links) = 62

• Referring Domains = 3 (only three different domains)

Why is this number important?

• 10 websites each giving you 1 link

• vs. 1 website giving you 10 links

Both cases have 10 backlinks, but:

• In the first case, Referring Domains = 10

• In the second, Referring Domains = 1

Google cares more about:

How many different sources are recommending you,
not just one site repeating your name over and over.

A simple practical mindset:

• When building links, don’t only take links from the same site again and again.

• Instead, try to get links from more high-quality, relevant websites.

3. What Are Sitewide Links?

Sitewide Link = A link that appears on almost every page of another website.

Common locations:

• Footer “friend links”

• Fixed blocks in the sidebar

• Main navigation or side menus

Example:

• Site B has 500 pages in total.

• You place a “Partner” link in its footer pointing to your site.

Result:

• Every page now has that link → you get 500 backlinks.

• But Referring Domains only increases by 1 (because they all come from site B).

Characteristics of sitewide links:

• They can push your backlink count up very quickly in a short time.

• But:

  • The link pattern looks less “natural”—in real life, it’s rare for every page to link to the same external site.

  • If the source site is low-quality, Google may treat these as spammy links.

Practical suggestions:

• A small number of sitewide links is okay, e.g., you and a partner site put each other’s logo in the footer.

• If you heavily rely on sitewide links to inflate your backlink numbers, you need to be careful—this may be seen as manipulating rankings.

4. What Is a PBN (Private Blog Network)?

PBN = Private Blog Network.

In plain language:

It’s a network of websites controlled by you (or your small team),
and their main purpose is to host links that boost your main site’s rankings.

How people usually do it:

1. Create or acquire multiple websites (different domains).

2. Put some content on each site so they look like “normal websites.”

3. Insert links in the content pointing to your main site, giving it a lot of backlinks.

Why do people use PBNs?

• You have full control over:

  • Which article links to you

  • What anchor text it uses

  • Which page on your main site it links to

• You don’t have to constantly ask others for links.

What are the risks?

From a search engine’s perspective:

One person controlling a bunch of sites whose main goal is to link to each other and boost rankings
is very likely to be treated as “unnatural links.”

If:

• Multiple sites use the same hosting IP, the same GA or Search Console accounts, similar themes, low-quality content, and heavily interlink with each other…

• Once they’re recognized as a link scheme, the entire network—including your main site—can be hit with penalties.

So the healthier mindset today is:

• Even if you use PBNs:

  • You should still make them look like real websites: clear topics, real content, actual visitors.

  • Outbound links should not be extreme, and anchor texts should look natural.

• If your goal is long-term, stable brand growth, many people now prefer:

  • Content marketing (writing good content that others naturally link to)

  • PR, partnerships, press releases

  • Guest posts and other methods to earn links.

5. How Do These Terms Work Together in Practice?

When you do SEO and analyze a website, you can think along these lines:

1. Check the backlinks

   • Get a rough idea of how much the site is being mentioned.

2. Check the Referring Domains

   • How many different websites are linking to it?

   • If Ref is low but backlinks are very high, you should suspect lots of sitewide links.

3. Look for sitewide patterns

   • If many links come from just a few websites, mostly from footer/sidebar,
     ask yourself whether those links are natural and how much risk they carry.

4. Evaluate whether PBN-like tactics are involved

   • Are the linking sites all heavily interlinking with each other?

   • Is the content thin and the topics all over the place?

   • If yes, you need to decide:

     • Is this just a short-term boost you’re willing to risk?

     • Or should you avoid working with this network to keep your main site safer?

6. Conclusion: Understanding the Terms Is the First Step in SEO

• Backlinks tell you how many links point to you.

• Referring Domains tell you how many different websites mention you.

• Sitewide Links describe a link pattern that can greatly inflate your link count.

• PBNs are a whole strategy of using multiple sites to manipulate links—powerful, but risky.

Once you understand these concepts, it becomes much easier to read reports and follow SEO discussions:
You’ll know which growth is natural, which is manipulated, which tactics fit long-term brand-building, and which ones you should treat carefully.