What is a Sprint Backlog?
Every iteration a Product Owner (customer) gets together with a team and tells them what product backlog items or requirements they want the team to work on for the next Sprint to turn into an increment of potentially shippable product functionality. The team takes these Product Backlog Items, as many as they think they can do in the next Sprint and they decompose them into the tasks required to produce the increment of potential shippable product functionality. These tasks are called the Sprint Backlog. This is an analogue to Lean Manufacturing where you only build a Sprint Backlog when a Product Backlog is presented to you and requested to be turned into an increment; so this is Just In Time Order Processing.