Going applying auditing database

Hello dear community members:

In the audit, I do not understand yet how it does Oracle.

Because if you restrict it to a user, then no audit and others?

Or should I say in detail commands all users to audit and non audit.?

I explain a little as I am understanding, if I can be put in a more or less clear.

a) In a case. - If I reduce my universe 2 users: Q1 and R1, and reduce my audit processes 2: A1 and A2. "-

I must run the commands as. -

a1) in the process Q1 A1 audited.

a2) Q1 audites not the process A2.