Scrum is a framework for developing products using an iterative approach with sprints. The key roles are the product owner, who manages the product backlog and maximizes ROI; the scrum master, who facilitates the scrum process and removes impediments; and the self-organizing development team of 4-9 people. The product backlog is an ordered list of features that is prioritized and estimated. Sprints are time boxed iterations, usually 2 weeks, where the team selects backlog items for the sprint and defines how they will be completed. Daily stand-up meetings allow the team to synchronize. At the end of each sprint there is a sprint review and retrospective to demonstrate work and improve the process.