Internal linking means the links between pages of the same site. It does three things at once: it makes pages discoverable, it distributes authority within the site, and it signals to search engines which content belongs together thematically.
Orphan pages
A page with no internal link pointing at it is practically invisible. It can be found through the sitemap, but it receives no authority, is fetched rarely, and ranks accordingly poorly. Orphan pages rarely arise deliberately — usually through automatically generated content, through navigation rebuilds, or because a cluster was created but never wired in. Checking for pages without an inbound link is therefore one of the most productive technical audits there is.
Click depth
The number of clicks from the home page to a page is a good indicator of its importance from a search engine’s perspective. What sits deep is treated as less important and visited less often. A flat structure in which every important page is reachable in a few steps therefore acts directly on discovery and ranking. On large corpora that is achieved through hub pages and cross-links, not through an overloaded navigation.
Anchor text
The text of a link tells the search engine what the target page is about. Descriptive anchor text is therefore considerably more effective than generic phrasing such as here or learn more. At the same time, moderation applies: a hundred internal links carrying the same exact anchor text reads as constructed. Natural variation naming the same topic differently is the better route.
Pillar and cluster
A proven pattern is bundling a topic: one comprehensive main page and several deepening articles that link both ways. The cluster articles point to the main page, the main page to all clusters. That structure makes the thematic relationship explicit and concentrates authority where it should rank — rather than spreading it across many equal-ranking single pages.
Why it belongs solved structurally
Maintaining internal links by hand works up to a few dozen pages. Beyond that, gaps inevitably appear, because nobody reviews every existing page for every new one. On larger corpora, linking therefore belongs derived from the data structure — through thematic relations, through category membership, or through a circular ordering that guarantees every page is linked from at least one other.
Practical consequence
Three figures suffice for an assessment: the number of pages with no inbound link, the number with only one, and the maximum click depth. If all three are low, internal linking is in order. If one is high, there is usually more unused potential there than in any external measure.