The difference between ‘do’ and ‘does’ is very basic. ‘Do’ is a verb (see Auxiliary Verbs), and ‘does’ is its third person singular present tense.

Thus, when the subject is represented by the pronouns ‘I’, ‘you’, ‘we’, or ‘they’, we must use ‘do’.

- I do not know the way.

- Do you know the way?

- We do not know the way.

- Do you they know the way?

On the other hand, when the subject is represented by the pronouns ‘he’, ‘she’ or ‘it’, we must use ‘does’.

- He does not know the way.

- She does not know the way.

- It does not look like the right way.