The core roles are those committed to producing the product:
Product Owner - The Product Owner represents the voice of the customer and is accountable for ensuring that the Team delivers value to the business. The Product Owner writes customer-centric items (typically user stories), prioritizes them, and adds them to the product backlog.
Team - The Team is responsible for delivering the product. They do the actual work (analyse, design, develop, test, technical communication, document, etc.). A Team should be self-organizing and self-led, but often work with some form of project or team management.
ScrumMaster - Scrum's facilitator. It's major task is removing impediments, enforce rules and protect the team while keeping them focused on the tasks at hand.
The project members assemble a Scrum Team consisting of 5–9 people . During discussions with the Product Owner, the goal of the Sprint is determined and the prioritized functionality is broken down into detailed tasks. The team is self-organized and the members have a joint responsibility for the results.
The Scrum Master coaches the development team, removes any possible impediments and constantly works to ensure that the team has the best possible circumstances for achieving the goals fixed for the Sprint.
Each Sprint enhances the product’s market value and adds new functions and improvements that can be delivered to the customer.