iChat is a third party AOL Instant Messenger (AOL IM) client, developed by Apple Inc. for the Mac OS X platform and first released with Mac OS X 10.2 on August 24, 2002. Fully endorsed by AOL, it uses their official implementation of the AOL IM protocols, as opposed to other third party AOL IM clients which use reverse engineered versions of the protocols.
It bears a brushed metal interface and uses speech bubbles and pictures that some advocates claim personify the online chatting experience.
In June 2003, Apple Inc. announced iChat AV Public Beta, a new version of iChat that added voice and video chat capabilities. It also introduced the iSight camera, designed specifically for use with iChat AV. These capabilities are based on the industry-standard, but not yet widely adopted, Session Initiation Protocol (SIP) for video chat and audio chat. The final version of the software was shipped with Mac OS X 10.3 and became available separately on the same day for users of Mac OS X 10.2 for USD 29.95. Apple eventually discontinued sale of iChat AV separately; it can now only be acquired through Panther or with a new Mac.
In February 2004, America Online introduced AOL Instant Messenger (AIM) version 5.5 for Windows-PC users. This version allowed video (but not voice) chats over the AIM protocol and was compatible with Apple's iChat AV. On the same day, Apple released iChat AV 2.1 Public Beta to allow Mac OS X users to video conference with AIM 5.5 users.
In June 2004, Steve Jobs revealed the next version of iChat AV that will be included with Mac OS X 10.4. This version will support up to four people in a video conference and ten people in an audio conference. Additionally, video conferencing will use H.264/AVC, which offers better quality than the current H.263. This release will also support the Jabber protocol.
See also: Jens Alfke - the initial developer of iChat