tl;dr
An approval flow is the sequence of reviews and sign-offs an invoice, expense, or journal entry passes through before it's paid or posted, typically routed by amount, department, or vendor.
Approval flows exist to enforce accountability, but they're also where AP work tends to stall: an invoice sitting in someone's inbox because they haven't gotten to it. Automating the routing, and letting an agent chase the approver or escalate a stale approval, keeps the control in place without letting it become the bottleneck.
See how this works in Light's Workflows.
