The difference and usage between do and does

The difference is:

Do is the prototype of the verb, which is used in the plural forms of the first person and the third person (I/you/us/them).

Does is used in the third person singular (he/she/it).

Do is used in the simple present tense, and the subjects are the plural we, them, you and i.

Does is used in the third person singular, he, she, it, etc.

Discrimination of examples:

First, do

What should I do?

What do you do?

What are you doing?

That's true.

They live there.

Second, whether

Maybe, he does.

Maybe he wants to fight.

He's not going.

He didn't go.

What's the use?