BitTorrent is a Communications Protocol of peer-to-peer file sharing, which is used to distribute data over the Internet. It enables fast downloading of large files using minimum Internet bandwidth.
BitTorrent maximizes transfer speed by gathering pieces of the file you want and downloading these pieces simultaneously from people who already have them. This process makes it easier to download large files like movies much faster than is possible with other protocols.
It was developed by Ben Cohen in 2001. The .torrent file holds all the information. The torrent descriptor has all the info about the encoding (I believe it still uses Bencoding, Bee-encoding), the chunk sizes, the SHA-256 value of each chunk, the MD5 value of the complete file etc plus much more too detailed to describe here.
It does not matter if a client gets all the different chunks from different people. In the end the chunks are combined together by the torrent client software and the original data is formed. Each and every chunk on receiving is compared with the hash of that chunk available in the .torrent file, which helps in keeping the integrity check of the whole file accurate.
