Bit Torrent is a popular P2P file sharing system. The BitTorrent network relies on Internet search engines that index files through metadata called torrents. Much like BitTorrent, eMule is another popular P2P file sharing software.
Bit Torrent client software allows files to be downloaded and uploaded on P2P networks using a high-performance network protocol. In a peer-to-peer network, peer who downloads the data also uploads it to other peers.
This makes spreading the files across the network easy & extremely fast without costing the original distributor additional bandwidth or hardware.