FTP

FTP (File Transfer Protocol) is a longstanding Internet protocol used to transfer files between Internet-connected systems. It actually predates basic Internet protocols such as TCP/IP and even the name "Internet" itself, and was used on the ARPAnet in the 1970s.

With the rise of the World Wide Web, it is less-used for one of its original purposes, of downloading files (such as programs and data) from remote sites, since HTTP can be used for that, but it is still widely used for uploading files to remote servers (something less well-supported by HTTP), and is often the way one gets Web pages live after developing them on a local computer. However, the increasing use of server-based web frameworks and environments, such as WordPress, is reducing the instances of creating and editing content on local PCs and sending them to a server by FTP, so usage is likely going down.

Specs, Standards, and Proposals

 * RFC 114
 * RFC 765
 * RFC 959 (official standard)
 * RFC 1639
 * RFC 2228
 * RFC 2389
 * RFC 2428
 * RFC 2640
 * RFC 3659
 * RFC 5797

Other links

 * Wikipedia article