IPFS InterPlanetary File System
Peer-to-peer protocol for content-addressed storage, started by Juan Benet (Protocol Labs) in 2015. You ask for what you want, not where it lives.
The address is a CID — a hash of the content — so the same file has the same address regardless of who stores it, and you can verify you got the right data. Files are split into blocks in a Merkle DAG, peers are found through a Kademlia DHT, and blocks are exchanged with the Bitswap protocol. Common misconception: IPFS does not store anything for you. Data survives only as long as some node pins it, which is the entire business model of services like Pinata and of Filecoin. Other objections: a CID changes on the slightest edit (hence IPNS and DNSLink), and most people end up going through a central gateway anyway.