Can and Could are used to express: ability, possibility, requests or asking for permission.

Explanations and some model conversations.

Welcome to twominenglish.com. Teaching you English through two-minute lessons. This lesson will help you learn the correct usage of ‘can’ and ‘could’.

Hello, Harris! Today’s lesson is about ‘can’ and ‘could’.
Can you tell me how to use them?
You’ve already started by using ‘can’. They’re used when one wants to express ability or possibility.
They are also used to make a request or ask for permission.
I used ‘can’ to make my request but ‘could’ is also valid. I could have said ‘Could you tell me how to use them?’.
That’s right! ‘Could’ is also used to express a past ability. For example: ‘I could run very fast when I was a kid’.
That’s a great example of ‘could’. Here’s an example of ‘can’: ‘There’s no need to run now because you can drive a car.’
Ha ha! Great example, Harris. So ‘could’ is for an ability in the past, and ‘can’ is for the present.
You can also use ‘can’ and ‘could’ to ask for permission, can’t you?
Sure. Here’s an example: Can I come to your place to watch the game tonight?
Oh, sure! I was looking for someone to watch it with. And you used ‘can’ to ask permission, right?
That’s absolutely correct! I will bring my jacket, it could be very cold.
That’s true. Did you use ‘could’ here to indicate the possibility that it might get colder?
Yeah, depending on the context, ‘could’ can indicate a possibility in the past or in the future.
I get it now! “I can swim” expresses my ability to swim while
 “I could not swim when I was a child.” expresses my lack of ability to swim in the past.
That’s brilliant! “Could you close the door for me?” is making a request while “Can I go home?” is asking for permission.
Yes, I see. Can we listen to some sample conversations now?
Sure. Here we go!

Hey Joe, could you pick up my dry cleaned clothes on the way home?
Yeah, I can do that. Can you close the door behind me?
Sure. Take your jacket, it could be snowing.
That’s right! Thanks dude.

Max, can you speak Spanish?
Yes. Why?
Martin needs some help in learning Spanish.
Oh, I guess I could help him out on the weekends.
That’s great. I’ll let him know.

REPEAT

I could run very fast when I was a kid.
I will bring my jacket, it could be very cold.
I can swim.
I could not swim when I was a child.
Could you close the door for me?
Yeah, I can do that.
Can you close the door behind me?