When you send e-mail, it bounces around the Internet until it hits the proper mail server where it sits in limbo until the recipient goes online to retrieve it. With IM you know almost instantly if someone is available while a phone will just ring on and on if no one's there to answer. And it's more discreet. You can send instant messages unobtrusively from meetings or classrooms where mobile phones might not be welcome. Sending instant messages can require a little linguistic creativity and dexterity if you're doing it from a small handheld.
Instant messaging is easy to set up and free.
Once you've downloaded the necessary software, you simply register with the service, choose a screen name, select a password and log on. If you want, you can submit a fairly detailed profile to the IM service including your age, gender, location, occupation, marital status and other information that will help others in the IM community with similar interests and status find you. You can personalize most IM programs as well. Some let you send customized icons such as a dancing cat or a grinning Bill Clinton to accompany your message. If all that sounds too good to be true, there is a hitch.