Stands for "Apple Filing Protocol." AFP is a protocol developed by Apple for sharing files over a network. It was used in early versions of Apple's Macintosh operating systems and is also supported in macOS 10. However, AFP has mostly been replaced by the standard SMB (Server Message Block) protocol.
Apple introduced AFP (originally the "AppleTalk Filing Protocol") with Macintosh System 6 in the late 1980s. It was part of the AppleTalk networking suite, which allowed Macs to communicate over a local network. AFP was also the foundational protocol used by AppleShare, a file server application. For several decades, AFP was the primary protocol used to share files between Macs.
In 2001, Apple released Mac OS X 10.0 and updated AFP to version 3.0 with significant changes. AFP 3 was the first version to support Unix privileges, files over 2 gigabytes, and UTF-8 filenames. The last update to the protocol was AFP 3.4, introduced with Mac OS 10.8 "Mountain Lion." Later versions of macOS have prioritized SMB as the primary protocol for file sharing.