There are 4 major IM networks that I'm aware of. I have nyms (accounts) on 3.
- AOL Instant Messenger (AIM).
- Google (GTalk).
- MSN / Windows Messenger.
- Yahoo Messenger.
Instant Messaging started out as a computer to computer text conversation, IVP / IRT. The various networks have added possibilities, and not all networks offer the same possibilities.
- Alert tool (buzz or nudge your friend, if he's not paying attention to the conversation).
- Audio (voice) conversation.
- File transfer.
- File sharing.
- Music sharing.
- Picture album sharing.
- Video (webcam) conversation.
And soon, you'll be able to IM your friends on Yahoo Messenger, from MSN / Windows Messenger, and vice versa. And in another trend, IRC now allows one - one (or restricted many - many) private chats.
As I said elsewhere, Instant Messaging started as a One To One relationship. It has evolved to Many To Many, and includes group chats, conferences, and whiteboards. IM group functionality further evolved into collaborative discussions and conferencing.