Before understanding sprint, we need to understand about Scrum. In implementing agile software development, there are popular frameworks like Scrum, XP or Kanban. Scrum is difficult to implement but the most popular framework for agile software development. Scrum team with around 5 members will be formed in this scrum framework for executing work.
Sprint is a time period set by the scrum team with a goal to complete particular work or to meet requirements at that time. Each sprint will have certain requirements to meet. This sprint will be around 3 to 4 weeks in general. The sprint time should not exceed one month because the process will become complex and cost may increase.
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You can check out this video to know more about sprint in Agile: