This page has been updated to Update #56.
The Oven bakes cookies while the game is closed.
You currently earn 10% of your CPS while away with whatever level Oven Baking Time increasing the total time away. Buying the 100% Oven Production for $13.99 CA or $9.99 USD will give you 100% Oven production.
If you have this game on an Amazon product, like a Kindle, the ovens and other in-game purchases are free, through the use of Amazon Underground.