To add to the previous answer:
GM crops are crops whose genomes are altered in order to reinforce their strong qualities, such as resistance to pestilence, ability to nourish, and others, and to rid them of any weakest links. There are lists of foods available in which one of the ingredients had been genetically modified to preserve their freshness, shelf life, consistency, and flavor. Most of these GM ingredients are found in frozen foods, packed snacks (such as tortilla and potato chips), and other products which require specific textures and tastes to appeal a market. Deductively, this shows how potatoes, corn, tomatoes and the likes, are the crops that are mostly GM'd for the purpose of being used for more popular foods as well.