Trying to understand a few financial terms?

Question

Is this correct

1) Purchase order (PO): Goes from customer to vendor.
2) Sales order (SO): Goes from vendor to customer
3) Invoice: Goes from vendor to customer

4) The order in which this happens is PO>SO>Invoice

Are statements 1,2,3,4 correct?
What is the difference between a SO and an Invoice?

Thank you

Answer 1

all of those documents can be explained in a lot more detail, but basically you are correct.

a sales order is something you give to a customer that details what they bought from you.

an invoice is the billing document that your customer will pay from.

Answer 2

invoice is a statement giving price and actually asking for payment.