What Is The Difference Between The Words, " Can & Could "?

Can and could are both what are called auxiliary verbs. We use can to talk about possibility and ability, make requests and ask for or give permission

We use could to talk about a past ability or possibility or to make requests.

There is a lot of difference between the English words Can and Could. The word can is used for present tense and for the action that can be done. E.g the sentence, "I can wash my clothes". Where the subject is concerned with doing of a task. Whereas the word could is used for past as you have mentioned above. Something that you could have done but you did not do. E.g I could wash my clothes.