"Apple's Instant Messaging client, iChat, includes support for direct peer-to-peer chatting without communicating via a server, using an XMPP-like communication protocol.
This mode, called "Bonjour Chat" in iChat, uses DNS-SD to discover peers with which to populate the Bonjour buddy list. This means that, unlike a conventional buddy list which you manage yourself, the Bonjour window gives you an automatically-created buddy list which can loosely be described as something like "people near me"."