Auxiliary Verbs are the verbs be, do, have, will when they are followed by another verb (the full verb) in order to form a question, a negative sentence, a compound tense or the passive.
23 auxiliary verbs:
do, does, did, has, have, had, is, am, are, was, were, be, being, been, may, must, might, should, could, would, shall, will, can. All other verbs are called lexical verbs.
The verbs be, do, have can be used as an auxiliary and a full verb. The verb will can only be used as an auxiliary. We use it to form the future tenses.
Auxiliary verbs can form a contraction with ‘not’
Lexical verbs cannot form a contraction with ‘not’