Auxiliary verbs are verbs that are used together with other verbs in a sentence.

For example:

I have given my granny some flowers for her birthday.

In this sentence 'have' is the auxiliary verb and 'given' is the main verb.

Forms of the auxiliary verbs 'be' (be/am/are/is/was/were/been/being) and 'have' (have/has/had/having) are used to show the tense of a sentence.

The children have been watching a film.

They were sitting on the sofa.

Now they have gone to bed.

Forms of the auxiliary verb 'do' (do/does/did) are used to change statements into questions and positive sentences into negative ones.

Do you like doughnuts?

Did he phone you yesterday?

Katie doesn't like sprouts.