Can is a modal verb. Lesson 27 shows you how to make correct sentences with it. This lesson shows you when you can use it.
She can speak good English.
Kiwis are birds but they cannot fly.
NOTICE: cannot is one word
Can you hear me?
I can't see anything. It's dark.
EXAMPLE: I'm afraid I can't see you this week but I can next week.
NOTICE: also be able to (Lesson 36)
EXAMPLE: Canada can be be very cold in the winter.
He can't be working now. It's much too late.
They can't have got lost. They know the way.
NOTICE: use must (Lesson 33) for strong probability
You cannot drive without a licence.
Passengers can smoke outside of the terminal.
NOTICE: more friendly than may (Lesson 30)
Can I borrow your pen?
Can I have the red one please?
NOTICE: could (Lesson 29) is more polite
Can you give me a hand?
Can you tell me the time?
Can I help you?
Can I get you some food?