Real-time chat is virtually any online communication that provides a real-time or live transmission of text messages from sender to receiver. A variety of software programs are available to enable real-time chat between individuals using Internet services.
Real-time chat can be any direct text-based or video-based (using webcams) one-to-one chat or one-to-many group chats by means of tools like instant messengers (IMs), talkers, Internet Relay Chat (IRC) and multi-user dungeons (MUDs).
Techopedia explains Real-Time Chat
The first real-time chat system was known as Talkomatic, developed by David R. Woolley and Doug Brown in 1973. It provided quite a few channels, each of which was able to support as many as five people, with messages from all users showing up on the screens character-by-character as they were typed. CompuServe CB Simulator, launched in 1980, was the first dedicated real-time chat service made available to the public.
Chat messages are often brief so as to let other participants respond swiftly, thereby creating a feeling much like a spoken conversation. This mode of communication differentiates real-time chats from other forms of text-based online communications, including emails and Internet forums. Real-time chat uses Web-based apps, which permit communication that is usually addressed directly but is anonymous among users in a multi-user environment.
Common real-time chat programs and protocols include:
AOL Instant Messenger (AIM)
Internet Relay Chat (IRC)
Windows Live Messenger
Chat programs that support multiple protocols include:
Websites having browser-based, real-time chat services include: