Baking is probably going to the first Hobby you are introduced to in The Sims FreePlay.
All you need to get going is a cooker! It's a pretty decent Hobby to start with and the are a whole plethora of things that you can bake. Because of any with a flame symbol next to them as there is a chance they will catch fire!
Each time you complete a baking task you are rewarded with not only the XP and Simoleans but also a collectible item. You have to collect these to swap them for other in-game rewards.