SFTP in computing terms refers to the SSH File Transfer Protocol, otherwise known as the Secure File Transfer Protocol, which is a network protocol designed to offer file management, file transfer, and file access functionality over any dependable data streams or channels. It's also a vast improvement from its predecessor, FTP (File Transfer Protocol), which used to be the standard in file transference between two computers during the dialup era and before the broadband era.
The SFTP standard was developed by the IETF (Internet Engineering Task Force) as an extension of the second version of the SSH (Secure Shell Protocol) in order to be compatible with a myriad of other protocols as well as provide users with secure file transfer capability. This specialized file transfer policy has become the gold standard in the file transferring protocol field in terms of excellence in service, security, safety, added intuitiveness, ease of use, and versatility, especially when considering the fact that it's quite usable with other protocols too.
The IETF claims that although SFTP is defined in the SSH2 protocol's context, it's a standard that's actually independent from the rest of the SSH2 protocol suite (so it's not limited by the SSH2's own concepts and definitions) and is even a lot more universal to boot. Because it can virtually be used with most other existing protocols, it can be applied into a multitude of purposes and functions, which may include the transfer of management information in VPN applications and secure file transfer over TLS (Transport Layer Security).
Whenever you open an SFTP application, you're required to enter the name of the SFTP host you want to visit as well as your password and username. All the authorized members of a given SFTP (a company's staff and crew or a university's student body and faculty, for example) can download and exchange files via either the WinSCP SFTP client for Windows PCs or the MacSFTP client for Macintosh machines.
SFTP assumes by default that it is running on a private and secure channel (e.g., SSH) wherein the server is authorized and deemed legitimate by the client. Moreover, the identity of the client user is accessible to the protocol. Also, the graphical equivalent of the SFTP client further abridges and streamlines the file transfer process by enabling you to deliver files via the tried-and-true drag and drop functions of your mouse; that is, just like in any standard propriety operating system, you can now access, copy, move, or paste files between windows using SFTP.