Auxiliary verbs help other verbs. The auxiliary verb comes before another verb and it shows the tense of the sentence, for example:

We can see the sun rising now. (present tense)

We could see the sun rising yesterday. (past tense)

We will see the sun rising tomorrow. (future tense)

Here is a list of auxiliary verbs:

am, are, be, can, could, had, has, have, is, may, might, must, shall, should, was, were, will, would.