(1) All the users connected to a single torrent. See
BitTorrent.
(2) (Swarm) A decentralized storage network that was designed for the Ethereum blockchain. Via distributed apps (dApps), Swarm stores data that would otherwise overload Ethereum, and transactions reference the data using a hashed key created in Swarm. IPFS is another storage system that complements blockchains, but Swarm was designed especially for Ethereum (see
IPFS).
Swarm has a built-in incentive system enforced via smart contracts and the BZZ token, which publishers spend to store data on the network. The Swarm storage architecture is called Distributed Immutable Store of Chunks (DISC). See
decentralized storage.