Chat

Real-time, synchronous communication: the core technology enabling instant, text-based, cross-platform message exchange between two or more users.

Chat, or Instant Messaging (IM), is a synchronous, computer-mediated communication technology, tracing its roots back to the 1960s with systems like MIT's CTSS. Its modern form was popularized by protocols like IRC and commercial clients such as ICQ (1996) and AOL Instant Messenger (AIM, 1997). Today's platforms (e.g., WhatsApp, Slack, Microsoft Teams) leverage various protocols (like WebSocket) to deliver immediate, two-way communication, far exceeding simple text: current IM systems integrate multimedia, file transfer, VoIP, and "presence" indicators. The technology is now foundational for both global consumer interaction (over 2 billion WhatsApp users) and enterprise collaboration.

https://en.wikipedia.org/wiki/Instant_messaging