A sprint is a fixed length of time during which the work of completing working software is completed. It begins with a sprint planning meeting and concludes with review and retrospective.
Common sprint lengths are one, two, three or four weeks. Some teams employ monthly sprints. No sprint should be longer than one month. Your team should choose the sprint length that works best for your particular situation.
Sprints divide the work into fixed iterations. At the end of each sprint, working software is delivered to the customer and the team works to refine and improve its process.