did –auxiliary verb

you –noun, subject

go –verb

Auxiliary verbs take precedence in determining number and tense

Helping verbs are:

1. v. to be

2. v. to have

3. Modals: will, must, can, etc

AND

4. v. to do

NOW

The first three are already there in a sentence:

He is reading a novel. What is he reading?

He has been reading this novel for a week now. How long has he been reading this novel?

He will start reading this novel next week. When will he start reading this novel?

BUT

He goes to school at 7.

The above sentence hasn’t got a helping verb (one of the first 3). To make a question we use v. to do (a dummy verb):

When does he go to school?

AND SO ON

He went to school at 7. When did he go to school?

They go to school at 7. When do they go to school?

I hope you have got it.

‘did’ acts as an auxiliary verb

‘you’ is of course noun

‘go’ is the verb