Cleaning an oven can involve common household items, like baking soda, vinegar, old toothbrushes (to scrape grime) or oxygen peroxide.
Cleaning professionals likely use a combination of these materials and their own when cleaning your oven. A common ingredient employed to clean ovens, sodium hydroxide, is toxic. Be careful if you choose to use this substance while cleaning on your own, but know that professionals will know how to be able to use it to clean without any hazard to you or your family!