BitTorrent is a peer-to-peer file-sharing protocol that is commonly used to distribute large amounts of data between multiple users.
Transmission is a BitTorrent client with an easy-to-use frontend on top a cross-platform backend. Native frontends are available for macOS and Windows, as well as command line and web frontends.
Notable features of Transmission include support for Local Peer Discovery, encryption, DHT, µTP, PEX and Magnet Link.