What is XMPP
XMPP is an XML-based instant messaging protocol. XMPP (originally “Jabber”) is open, anyone can create a client that can communicate via the protocol, in fact, there are many software (clients) with which you can use it.
The architecture of the XMPP network is similar to email. There are no dominant central servers (it is decentralized) and anyone can make their own XMPP server. It is a federated system, that is, all servers communicate with each other without the need to belong to the same service provider. Just as in the case of e-mail: you can register with any service provider and write to anyone with an XMPP address using the programs you prefer. The service provider (server) is indicated by the part that comes after the `@` in your JID (Jabber ID) address.
XMPP is one of the very few messaging systems not in the corporate hands.
The core specifications for XMPP are developed at the Internet Engineering Task Force (IETF), instead the XMPP Standards Foundation (XSF) develops extensions to XMPP in its XEP series.