What are the difference roles in Agile?

 There are at least 3 roles in Agile: product owner, scrum master and the development team.

1. The product owner: Setting clear direction

Scrum product owners understand the customer and business requirements, and then create and manage the product backlog based on those requirements. 

The Scrum Guide defines the product owner's responsibilities as:

• Managing the scrum backlog 
• Release management 
• Stakeholder management 

2. The scrum master: Holding it all together

The scrum master is the role responsible for gluing everything together and ensuring that scrum is being done well. They help the product owner define value, the development team deliver the value, and the scrum team to get better. 

They serve the product owner by helping them better understand and communicate value, to manage the backlog, help them plan the work with the team, and break down that work to deliver the most effective learning. Serving the development team, the scrum master helps them self-organize, focus on outcomes, get to a “done increment,” and manage blockers. The scrum master also serves the organization at large, helping them understand what scrum is and create an environment that supports scrum.

The scrum master serves the product owner in sprint planning and sprint reviews, ensuring that value is clearly being described and direction set. They serve the development team in the daily scrum by ensuring that work is happening and that blockers are being removed. They also take responsibility for blockers that are outside of the team's ability to resolve. The scrum master ensures that every opportunity to improve is made transparent to the scrum team and the retrospective has a clear set of outcomes that can be executed.

3. The development team: Redefining “developer”

The development team includes the people that do the work. The development team can be comprised of all kinds of people including designers, writers, programmers, etc.  

The development team’s responsibilities include:

• Delivering the work through the sprint.
• To ensure transparency during the sprint they meet daily at the daily scrum (standup). The daily scrum provides transparency to the work and provides a dedicated place for team members to seek help, talk about success, and highlight issues and blockers. The scrum master might facilitate the daily scrum, but ultimately it is the responsibility of the development team to run this meeting. It is their meeting to help them, as a group, to inspect and adapt the work they are doing and work more effectively.