A torrent, is a computer file that contains metadata about files and folders that are used for distribution to a larger group. These are often used with large files and are shared between large groups of people, often for work related purposes. Files are usually named with the ".torrent" extension after the file's name.
Torrent files only contain information about files: their name, sizes, cryptographic hash values and folder structure. Additionally, they contain a list of the network locations of the trackers. This enables participants to find each other efficiently and create groups, called swarms, that distribute the information quickly and effortlessly. There's usually no content inside the torrent file itself.
Since torrents fall in a relatively unregulated area of use, the use of torrents is a hot topic, getting plenty of media attention in cases of torrents being used for sharing illicit data. Used as designed, for easier peer-to-peer sharing of data, they are legal to use.