"IM" – short for “instant messaging” – is a real-time communication service between desktop computers. IM has evolved from the public online chat rooms of the 1990's and 2000's, and become quite sophisticated and very common. IM is even used as productivity software in many companies. Some of the big IM players include Microsoft Lync, Trillian, Brosix, Digsby, AIM, Gtalk, and Nimbuzz.
IM desktop software works somewhat like email and smartphone text messaging, but with the speed of a private chat room. Both parties are online at the same time, and they "talk" to each other by typing text and sending small pictures in instantaneous time.
IM is based on special small programs that two separate people install, and those programs connect to beam typed messages to each other. This special software allows you to message your online friends in other rooms, other cities, and even other countries. The software uses the same cables and network as any web page or email connection. As long as the other person has compatible IM software, IM works very well. Some IM tools even have "you've got mail" capability, where you can send messages while the other person is offline, and they retrieve it later like email.
For teenagers, IM is a way to break boredom in the school computer lab...provided, of course, that the teacher doesn't shut down the IM connections in the room.
On the downside, many companies do forbid employees from using IM because it can be such a distraction to employees. Thousands of people every day steal time away from work to chat with their friends and co-workers on their screens. On the upside, some organizations do legitimately use this social tool to communicate, like receptionists talking to their bosses on-screen while simultaneously speaking on the phone. Factory workers who wear ear protectors can see on their screen when their supervisor needs them on the other side of the factory floor.
There are varying levels of IM sophistication. Some IM products are bare-bones (example: Google Talk). You can simply send text messages only.
Other IM systems offer advanced options that let you do more than send text messages. It is possible to share photos, send and receive computer files, carry out web searches, listen to the Internet radio stations, play online games, share live video (requires webcam), or even place free PC-to-PC calls worldwide if you have the speaker-and-microphone hardware.
Next: How IM Works (and How to Get It Installed)...