IPFS, a hypermedia peer to peer protocol. In short, all the files are stored on nodes on IPFS. Sort of like how torrents work
The files are on many computers (nodes) belonging to other people (peers)
IPFS can be fast because you can potentially find users close to you on the map meaning file transfer will take a short time
They would also be sending you the files at the same time, meaning you would get the files really fast