This can get really detailed and granular so I'm going to keep it at a high level, but the key is that you cannot have foods with leavening (known as chametz) during Passover. Depending on how strictly you keep Kosher for Passover, you may look for ingredients that are specifically labeled Kosher for Passover, but I am less stringent and simply ensure there are no grains or other Passover-prohibited ingredients in any products I buy.