"Auxiliary verb" OR "Helping verb"

An Auxiliary verb or Helping verb such as be, do and have used with main verbs to show tense, etc. and to form questions and negatives.

For Example:

I am eating food.

I have written a latter.

He did not watch T.V.

In the above tenses Helping verbs are "am, have and did" they are all showing the time and period 1st tense is talking about middle of action"eating" and 2nd tense is talking about something has done before but it is connected with the present like the tense " I have written a latter" says someone wrote a latter in the past but the latter is still in the hand of that person. And the last one talks about totally past like something happened in the past and there is no connection with it. Like " I ate food six hours ago now I am hungry." its mean there is no more food in his stomach.