Can and can't are used to express ability or inability to do something, such as "I can play the piano" or "I can't play the guitar". Can and cannot are also used to ask and give permission, like "Can I go to the bathroom?" or "No, you can't". Additionally, can is used to make requests and offers, for example "Can you close the door?" to request something or "Can I help you?" to offer assistance.

1. CAN AND CAN’T, CANNOT
THE USE OF CAN:
To express ability: we use to express that we
know how to do something.
Can and can’t always is followed by a verb in
infinitive
Example: I can play the piano, but I can’t
play the guitar
To ask permission: we alsouse can and
cannot to ask and give permission
Examples:
a) Can I go to the toilet, please?
Yes, you can
b) Can I go to the bathroom?
No, you can’t
Requests and offers: we use “can” to ask
somebody to do something
Example:Can you close the door, please?
Can you pass me some water?
Can you borrow your notebook, please?
To offer to do something
Example: Can I help you?
Can you give me a hand?