Can is a common word with two main meanings:

1. A metal container, usually cylindrical, used to hold food, drinks, or other materials. You might open a can of soup for lunch or recycle aluminum cans after drinking soda. Foods stored in cans stay fresh for months or even years because the canning process seals out air and bacteria. When you can fruits or vegetables (used as a verb), you preserve them by sealing them in containers. Before refrigeration became common, canning was one of the most important ways to keep food from spoiling.
2. To be able to do something. When you say “I can swim,” you mean you have the ability or skill to swim. When your teacher says “you can go to recess,” she's giving you permission. The word indicates both ability (“Can you reach that shelf?”) and possibility (“We can finish this project by Friday if we work together”).

People sometimes confuse can with may when asking permission. Technically, “Can I go to the bathroom?” asks about ability, while “May I go to the bathroom?” asks for permission, though in everyday conversation, both are widely understood and accepted.