BitTorrent is a peer-to-peer protocol for distributed file sharing that allows users to download files from multiple other users simultaneously. It addresses issues with traditional client-server and multicast models by using a "pull" model where nodes request pieces of files from peers rather than receiving sequential pushes. Nodes are incentivized to upload through a tit-for-tat approach. The protocol became widely popular due to its performance advantages over previous P2P systems and its ability to utilize partially downloaded files from many sources. While it relies on centralized trackers, modified versions use distributed hash tables to operate without them.