1. What is a three-way match?
Before you pay a supplier, three documents have to agree: the invoice (what they're charging you), the purchase order (what you agreed to buy), and the goods-received note (proof you actually got it). Checking that the three line up is the “three-way match.”
Today a person does it by hand, one invoice at a time, across every format an invoice can arrive in. This agent does it for them, and posts the clean ones straight into your finance system.