For the community's dictionary
CAW is the short version of Create A World and it refers to the Create a World tool for The Sims 3. It's a separate, free program that was released in a beta version in order to let players build and create their own world for The Sims 3 from scratch.
For more information on the Create a World tool, you can check out The Sims 3's website where you can also download it:
Please note that this program is for The Sims 3 only and the worlds you create in it doesn't work with any other The Sims-game.