This question was asked by the community, and though I'm sure this might refer to sites like Twitter or Facebook, social online communities existed well before the social networks we know today. In the late 80s and early 90s, BBS (Bulletin Board Systems) were set up by enthusiasts and opened up for people to connect to through a modem connection. Back then, modems were considerably slower. A 2400 baud modem was common during the height of BBS popularity, and only folks with a good amount of disposable income went for the only slightly faster 9600 baud speed modems.
When logged in to a BBS, you were able to do all kinds of things. You could play games (referred to as door games), which were generally multiplayer and allowed you to play with and/or against other people. Trade Wars 2002 (still playable in some places online) was the most popular of these games, giving users the ability to pilot starships in a Star Trek parody environment. Graphics were rare, and the ones that you did find were ASCII art (a method of using text to create an image).
Through a BBS, you could also send and receive a form of email, leave messages on forums hosted on the BBS, download software and images, and more.
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