What is a helping verb?

A helping verb is used with a main verb in a sentence.

For example:
He does not play soccer.
- In this sentence the main verb is "play" and the helping verb is "does"

For example:

Lisa does not go to school.
not
Lisa does not goes to school.

​If a sentence has helping verbs they should be conjugated but the main verb should be left in the base form.

Note: statement sentences in the negative use helping verbs.

For example:
We don't like hamburgers.
- In this sentence the main verb is "like" and the helping verb is "don't"
However, in the positive only the main verb is needed.
We like hamburgers.

For example:

Yesterday I did not eat breakfast.

not
Yesterday, I did not ate breakfast.

​In a past tense sentence only the helping verb is conjugated in the past tense