Short version: A checkout flow is the full sequence of steps a customer goes through from cart to completed order.
It includes the cart transition, contact form, delivery choices, billing details, payment, validation messages, review step, order placement, and confirmation. The flow can be one page, several steps, or a guided sequence, but the real measure is whether customers can finish without doubt, delay, or unnecessary work.
Improving a checkout flow usually means finding where people drop off and why. Hidden costs, unclear shipping, forced accounts, too many fields, weak trust signals, payment issues, and confusing errors can all interrupt the purchase. The goal is not to remove every detail, but to keep only the details that help the order happen safely.
Related terms: checkout, cart, and abandoned cart.