It's primary goal is a free-to-use Game creator using blocks for creating and Lua to script.
It's fun if you know what games to play, and have experience/time to create a game. The Community is usually the worst as it's filled with younger kids (Although I have made two good friends thanks to this site)
The game can be vastly different from Minecraft, using the studio you can create virtually anything you want (Yes, even curves if you know how) I have seen everything from RPG's to Diablo-styled dungeon crawlers, hell, there's even a Wheel-of-fortune game with decently good voice acting (which is rare and expensive for Roblox games)

Ok, Rant over, you can go about your day