Process Order fields

Hello

I'm basically new to PP-PI and could anyone explain me the process flow.

1.when we create process order what the fields Total quantity, Delivered and Expected Yield Variance means.

2. should we do confirmation of process order to get in to process(production) or when we save process order means that it can go in process(production).then why do we need to confirm or is it like a goods receip in MM for Purch Order?

3. where do the data stores(table and field) for the output for the process order.

4. If we want to check that how much quantity was scheduled to produce and how is actually produced and whats the variance......where do we look this data.

Can you please explain me ASAP as it very urgent and important to me.

Thank you in Advance

Mittu