To cater means to supply food for meetings or celebrations. If you're having a big barbecue party but would rather hang out with your friends than grill, you could pay someone to cater it.
In Middle English, the food supply in a big household was known as the cates, and so to cater meant keeping the pantry full. These days, caterers don't do pantries. They cook food for many different households or offices. Cater has also come to mean "giving what is desired or needed." You might cater to your grandfather by bringing him tea, reading to him, and laughing at his bad jokes.