The File Transfer Protocol (FTP) is the system by which data is transferred between computers. This protocol works in the background of most file transfers on the internet, which will feature user-friendly interfaces on the front-end. It needs two parties established and communicates via a network. Normally there will need to be permission granted by both parties, though some public servers may not require credentials to access documents.
FTP is also the protocol used by Unix systems. These systems run by the inputting of textual commands at the command prompt. Among the most popular of these FTP systems are FileZilla and Core FTP LE.