The File Transfer Protocol (FTP) enables the transfer of files between computers over a network. It works similarly to a mail service: one computer sends files to or receives files from another computer. There are two main types of connections: active and passive transfer. FTP can be used for both uploading and downloading files.

FTP has long been the standard protocol for exchanging files over networks. It's robust but insecure: data, including passwords, is transmitted in plain text. FTP functions like a virtual mail service for files—with logging, listing, and transferring. However, FTP is an unencrypted protocol, meaning the transferred data is sent over the network in plain text. For this reason, the more secure variant, FTPS, is recommended, as it uses SSL/TLS for encryption, thus ensuring secure file transfer.

Still useful today? In its pure form, hardly—FTPS or SFTP (over SSH) are preferred today because they offer encryption. Many modern services have replaced FTP entirely.

Classification in the OSI model:

• Application Layer (Layer 7)
  FTP works at the application layer and allows interaction with files transferred between computers.