Instant messaging systems allow people to exchange short text messages. Unlike email, they are designed for to-and-fro interactions between people. The first instant messaging system was born in 1965.
Texting/SMS on mobile phones is similar to basic instant messaging. Both send simple, short text messages. However, texting/SMS works specifically with mobile phones. Instant messaging usually has far more functionality and works between computers over the internet.
Presence information, showing people's online/offline status, is typically tightly integrated with instant messaging systems.
Instant messaging functionality has expanded from its early days, so that nowadays some level of rich text is supported, along with such things as presence information, voice calls, video, screen sharing, and file transfers.
Standards have been defined to provide for interoperability of different instant messaging systems. However, most instant messaging systems have only limited abilities to work with other instant messaging systems. Perhaps interoperability will be in place by 2019.
As of 2012:
- The leading instant messaging services are AOL Instant Messenger, Facetime, Google Talk, ICQ, Skype, Windows Live Messenger and Yahoo! Messenger
- The leading on-premises instant messaging software products are IBM Lotus Sametime and Microsoft Office Communications Server.
--David Ferris