Can means be able to or permitted to do something. Could refers to the possibility or the ability to do something.
How do you use can could and be able to?
Be able to is possible in all tenses – but “can” is possible only in the present and “could” is possible only in the past for ability. In addition, “can” and “could” have no infinitive form. So we use be able to when we want to use other tenses or the infinitive.
Would be able to VS could?
Could and would are related, but they mean different things. Could expresses possibility, while would expresses certainty and intent. A good way to remember the differences between these two words is simply to bring each word back to its root verb. Could is the past tense of can.