A can is a metal container, usually cylindrical in shape, which has an airtight seal when it's new. All kinds of goods come in cans, from fruit and vegetables to paint and oil.
The verb can means to preserve food in a can or glass jar. If your garden produces more tomatoes than you can possibly eat, you might make salsa and can it to eat all winter long. Can is also a slang word with several meanings. It means rear end, toilet, and it also means to fire someone: "Watch out, the boss canned three people yesterday! You could be next."