Internal linking is the practice of linking between pages on the same site — from a blog post to a product page, from a category to a child SKU, from a footer to a deep topical hub. Distinct from external linking (outbound to other domains) and backlinks (inbound from other domains), internal linking is the under-leveraged signal most operators ignore.
For SEO, internal linking does three things. (1) Distributes PageRank from authority-rich pages to authority-poor pages. (2) Helps Googlebot and AI crawlers discover content efficiently — without internal links, the sitemap is the only discovery path. (3) Signals topical authority by clustering related content with descriptive anchor text.
For AEO, internal linking matters more than for classic SEO. AI crawlers follow internal links to map your topical authority graph; pages that link to and are linked from related authoritative content cite more reliably. Orphan pages (no internal links pointing to them) get marginalized by AI engines even when their content is strong.
The high-leverage tactic is the "pillar + cluster" pattern: one authoritative pillar page per topic, surrounded by 10-30 cluster pages that link UP to the pillar (and the pillar links DOWN to all of them). The whole cluster reinforces topical authority on the pillar's primary keyword.