What it is
Internal links are links from one page on your site to another page on the same site. A link from a blog post to a product page, or from a hub to its sub-articles, is internal linking. The words you use in the link, the anchor text, tell readers and machines what the destination is about.
Why it matters
Internal linking serves all three audiences at once. People get a clear path through your content. Search engines follow the links to discover pages and infer which ones you treat as important. AI systems use the same structure to understand how your topics connect, which supports being seen as an authority on a subject rather than a single stray page.
What to do
Link new content to your most important related pages, using descriptive anchor text instead of click here. Build topic hubs that link out to detailed pages and back, and fix orphan pages that nothing links to.