ABILITY: (to be able to)
- Can you drive?
- Can you play the piano?
- Can you speak French?
PERMISSION: (to be allowed to)
- You can park here.
- You can hang your jacket up in the closet.
- You can have dessert if you finish your peas!
REQUEST: (informal requests)
- Can you tell John that I'll pick him up at noon?
- Can you close the window, please. I'm cold!
POSSIBILITY: (possibilities in the present, not in the future)
- You can find the information in a dictionary.
- You can order a beer when you are 21.
OFFER: (polite offers of help)
- Can I help you with those boxes?
- Can I help you finish the project?
Courtesy of and adapted from Cambridge Advanced Learner's Dictionary.