Two things share a popular name and play very different parts. Confusing them leads to a common waste: earning links from outside with great effort and leaving them stuck on a single page.
Backlink: it comes from outside
Another site points at yours. It is a third party’s recommendation, and that is why it weighs: you do not control it, so faking it is hard.
Internal link: it connects your own pages
You control it entirely, and it does three things:
- Helps the search engine find your pages. A page no link points to is an orphan, and may never be discovered;
- Spreads the reputation that arrived from outside. If your home page got ten backlinks, it is the internal links that carry part of that strength to the pages that sell;
- Explains the hierarchy. What receives links from everywhere is understood to be important.
The common waste
Many sites concentrate every backlink on the home page and never link the home page to the pages that matter. The reputation arrives and stops there.
Fixing it is cheap: from the home page, point at the main pages; from each article, point at the guide on the subject. No new link from outside is needed — only using what already came in.
In practice
Backlinks are hard to get and you do not control them. Internal links are free and entirely yours. Anyone chasing the first while ignoring the second is paying dearly for something they are then throwing away.
