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.
Yeah that was part of the brand reshuffling they did to obfuscate things. Lync was their shitty chat app they tried to convince businesses to use that everyone hated. They bought Skype, renamed it to Microsoft Teams, renamed Lync to Skype for Business, and killed MSN Messenger. When people still didn't want to use LyncSkype for Business, then they killed that as well, and now it's just MS Teams.
Fun fact any developer working with the api can tell you, there is a clear distinction between de voip bit and the meeting/chat bit. They haven't bothered rewriting or integrating it in any way so the Skype for business backend is still very much alive.
Another fun fact: On the backend, Teams uses SharePoint to store files, and Exchange to store message. The whole M365 stack is a house of cards built on ancient tech. It's a wonder it works at all.
Still remember setting up lync 2013 for our company. It was one of the funner projects I remember doing. I was not as thrilled about setting up SharePoint 2013....