is it JUST a place for fans to post/make missions?? is it a squad builder? just wondering just what it its and what it is used for.. obviously i haven't messed with it... Thanks

Mostly it's fan-made missions. FFG also put up a few.

There's a lot of missions out there but it's a little hard to find one that you like. Some are pretty well-written, some aren't. Some are serious, others are just for fun. I put up a 'guide to mission control' (linked in signature), where I go on like a windbag for a long time about how to write missions, etc. you may find some of that interesting. I also put out a list of well-written missions (at least by my standards), so browsing is a little easier.