In the BitTorrent file distribution system, a torrent file is a computer file that contains metadata about files and folders to be distributed, and usually also a list of the network locations of trackers, which are computers that help participants in the system find each other and form efficient distribution groups called swarms. A torrent file does not contain the content to be distributed; it only contains information about those files, such as their names, sizes, folder structure, and cryptographic hash values for verifying file integrity. Depending on context, a torrent may be the torrent file or the referenced content.
Torrent files are normally named with the extension .torrent.
MORE INFORMATION/SOURCE : https://en.wikipedia.org/wiki/Torrent_file