It's as Douglas said. I have worked in a few places (which were often business canteen type places) where the workers are employed by a third party company who have won the bid to provide the food. So its pretty much the skills you already have from restaurants, plus a much more stringent recording regime to prove food was always kept at temperature, disposed of after the relevant amount of time, waste recorded etc etc. It's used to prove you are sticking to the contract and to help make a new bid if the contract comes up for review.