The Extensible Messaging and Presence Protocol (XMPP) is an open-standard communication protocol designed for real-time messaging and presence information. It allows users to send messages, share their online status, and engage in group chats. XMPP is widely used in various applications, including instant messaging and online gaming, due to its flexibility and extensibility. XMPP operates over the Internet using XML (eXtensible Markup Language) for data exchange, making it easy to integrate with other systems. It supports various features like file transfer and voice/video calls, and is the foundation for many popular messaging platforms, including Google Talk and WhatsApp.