Freenet is a peer-to-peer network where content is stored in encrypted chunks distributed across all participating nodes. When you publish a document or website on Freenet, it is broken into encrypted pieces and spread across the network. No single node holds the complete content, and nodes do not know what they are storing because everything is encrypted.
Content on Freenet persists as long as it is popular - frequently accessed content is cached by more nodes and remains available longer. Unpopular content gradually disappears as nodes reclaim storage space. This means Freenet is excellent for widely distributed content but less reliable for niche or infrequently accessed material.
Freenet offers two modes: Opennet (connect to any node, easier but less secure) and Darknet (connect only to trusted friends, harder to set up but much more resistant to surveillance). Darknet Freenet is one of the most surveillance-resistant communication tools available, as the network topology is invisible to outsiders.