That is, an MMORPG before the days of graphics. Like Zork (for those who remember) with multiple people playing at the same time.
I fooled around on some of the TF ones. Lot of fun, but it was my freshman year and I honestly had other things I was into more. Looked around for one a few months ago, but don't think there are any active TF ones.
I played one called Realms of the Dragon, for a few months. It was a lot of fun, at a time when there weren't any MMORs.