Pieces are downloaded in a seemingly random order based on which peers have them and which are fastest to provide them.
Each piece has a unique cryptographic hash (SHA-1) in the torrent file, allowing the client to verify every segment for integrity as it arrives. Benefits of Fragmented Downloading Fragmented Torrent Download
A large file is divided into numerous small segments called pieces . Pieces are downloaded in a seemingly random order
The process relies on a distributed network rather than a central server: Fragmented Torrent Download