There are two classes of verbs in English. The auxiliary verbs (helping verbs) like to be, to have and to do, may, can, might, could etc.  All other verbs which denote actions are the main verbs (ordinary verbs) like to sing, to play, to look, to work etc.

to be, to have and to do are principal auxiliaries. Their different forms are:

(Infinitive)           (Present tense)            (Past tense)                (Past Participle)

to be                      am, is, are                       was, were                     been

to have                  has, have                         had                               had

to do                      do, does                          did                               done

 

First person: I am, I have, I do, I was, I had, I did, We are, We have, We do, We were, We had, We did

Second person: You are, You have, You do, You were, You had, You did

Third person: He/She is, He/She has, He/She does, He/She was, He/She had, He/She did, They are, They have, They do, They were, They had, They did

Singular subject takes is, was, has, had, does, did

Plural subject takes are, were, have, had, do, did

e.g. It is beautiful.

The shoes are dirty.

The bag has many pockets.

The insects have six legs.