Could: The word Could is indicate the possibility of something. You can use this word to describe whatever you are telling has the possibility of a similar result.
It says you are not sure about the final result but you can assume that it will go in the direction you are expecting to go.
The other way to use the word “could” is requesting something from others. If you want to borrow a phone from your friend then you can ask them “Could I use the phone?”. It is requesting form of asking someone to provide their phone.
In another word you are asking “Is it possible to use your phone?”.
Here are some of the example of using could in the sentences.
1) The person could be right
Describes: The information shared by the person might be correct. You are not sure about it.
2) Could I use your phone?
Describes: You may want to do urgent call, but you don’t have your phone, so you are requesting someone to provide their phone to have one phone call.
3) They could have told me!
Describes: Your friends went for the movie, but they did not inform you and you got to know from another friend who is not with them. That time you may have the reaction “They could have told me.”
This explains you are expecting your friend should have told you before going to the movie, so you might have joined them.
