The following diagram summarizes the key steps in an Agile development process:
where the numbered steps are as follows:
The length of a sprint is typically between one and four weeks and is usually fixed for the duration of a project.
During each sprint, developers take items from the sprint backlog, work on them, and complete them by the end of the sprint.
At the end of each sprint, the items on that sprint's backlog must be completed; not just coded, but tested, documented, and integrated into a working product that could be deployed (if required).
At the end of a sprint you return to the Agile planning stage to create the next sprint backlog.
At the end of the project you return to the requirements gathering stage to create the new product backlog.