Instant messaging, or IM, is a form of text communication between two or more people in ‘real time’ while online. It's similar to email but with the speed and immediacy of a phone conversation. It's also similar to a chat room, but with greater privacy as you can select those involved in the text conversation. You do this by creating a list of contacts or 'buddies' – you'll be alerted when they're online at the same time as you.