Actually, ICQ uses a direct connection between users to send messages, unless you go to the Preferences dialog and specifically tell it that it should send messages through the server. And, even then, files will still be sent directly. AFAIK, you can not store files on an ICQ server.
Since nobody else could be bothered to list them, here are a few of ICQ's features:
- Instant Messages (of course)
- Shows when other users on your contact list are online (assuming they are not in invisible mode)
- Invisible mode, so others can not see that you are online
- Invisible list, so you can specify specific people who can not see when you are online
- Ignore list
- URLs (so you lazy people can just click a button rather than copying a URL to the clipboard and pasting it into your web browser)
- External application support (so you could, for example, start Netmeeting with another user right from ICQ with just a couple clicks)
- File sending
- User groups (so you can make a group for your friends, a group for your enemies, a group for artichokes, &c)
- External plugin support
- Comes with voice-chat plugin
- Real-time text-chat (by that, I mean you see what a person is typing as (s)he types it) or, if you prefer, IRC-style chat. Supports as many users at once as you have bandwidth for.
- Custimizable sound events
- With ICQ Plus, you can skin it
My UIN is 708960,
ICYC.