It was the late 90s, social media platforms like Facebook didn't yet exist, texting was in its infancy, email was very popular, instant messaging was up for...
The bottom of the article links to the history (individual features) of other IM programs from that era as well like ICQ and Yahoo Messenger.
It was awesome. Especially paired with the msn messenger plus mod.
Near the end of its time and also when WiFi was taking off, I had friends with everyone in a uni house, but their WiFi was quite unreliable, so every hour or so I'd get 6 "person is online" pop up toasts appear simultaneously, stacked up on top of each other.