Agile projects are broken down into sprints or iterations — short, repeatable phases, typically one to four weeks long. The number and length of the sprints should be determined at the beginning of the project, and each sprint should result in a draft, prototype, or workable version of the final deliverable.
Sprints break down a project into bite-sized chunks. Teams plan a single sprint at a time and adapt future sprints based on the outcome of the previous one.
While each sprint is planned separately, the number and length of sprints in your project should be determined at the beginning.