More advanced integrations may wish to implement an authorize-then-capture flow. In such a scenario, the customer already authorizes a payment up front, and at a later point you may either capture (i.e. charge) the authorized amount or cancel it. In some scenarios, you may also capture a different amount than initially authorized. For more information see Place a hold for a payment.
The Captures API can only be used for payments created with the Payments API. Use the Shipments API to capture Orders.