Sims Carnival is a Flash Game Creator that allows you make simple games by allowing you to remake the set of games in the site. you can change images, customize the inner working of the games, etc. all by using a question based selection settings and by having easy to use modules in the game editor. it also allows for some drag and drop experiences that ensure that anyone can create a game.
The rationale of using the sims brand seems to be that these user created and sim carnival official games will be able to interact with The Sims franchise. details on that are yet unknown.
The best of this creator if you are not into the sims is that you can take your game with you. you can embed it in your blog and use it without having to worry about anything else.
If you are interested in the sims games, then it would be good for you to know that there is a $1000 dlls contest to make the best sims carnival game.