The XMPP protocol allows for asynchronous communication over an open XML-based protocol. It was invented in 1998 as the Jabber protocol and standardized by the IETF as XMPP in 2004. XMPP supports messaging, presence, and request-response services and can be used for applications like instant messaging, collaboration, gaming, and more. It uses XML stanzas sent over TCP, BOSH, or WebSockets and supports features like federation, group chat, and VOIP calling.