Popular Agile Method - Scrum

• 
  Scrum is an iterative, incremental framework for projects and product or application
  development. It structures development in cycles of work called Sprints. These iterations are no more than one month each, and take place one after the other without pause. The Sprints are timeboxed – they end on a specific date whether the work has been completed or not, and
  are never extended.
  

Scrum Roles
In Scrum, there are three roles:

• The Product Owner
• The Team
• The ScrumMaster.

Together these are known as The Scrum Team.

The Product Owner is responsible :
For maximizing return on investment (ROI) by identifying product features, translating these into a prioritized list.
Deciding which should be at the top of the list for the next Sprint, and continually re-prioritizing and refining the list.
The Product Owner has profit and loss responsibility for the product, assuming it is a commercial product.
In case of an internal application, the Product Owner is not responsible for ROI in the sense of a commercial product (that will generate revenue), but they are still responsible for maximizing ROI in the sense of choosing – each Sprint – the highest-business-value lowest-cost items.

The Team builds the product that the Product Owner indicates
The Team in Scrum is “cross-functional” – it includes all the expertise necessary
to deliver the potentially shippable product each Sprint – and it is “self-organizing” (selfmanaging).
With a very high degree of autonomy and accountability. The Team decides what to
commit to, and how best to accomplish that commitment
The Team in Scrum is seven plus or minus two people, and for a software product the Team might include people with skills in analysis, development, testing, interface design, database design, architecture, documentation, and so on

The ScrumMaster helps the product group learn and apply Scrum to achieve business value.
The ScrumMaster does whatever is in their power to help the Team and Product Owner be
successful.
The ScrumMaster is not the manager of the Team or a project manager; instead, the
ScrumMaster serves the Team, protects them from outside interference, and educates and guides the Product Owner and the Team in the skillful use of Scrum.

In addition to these three roles, there are other contributors to the success of the product, including functional managers (for example, an engineering manager).

While their role changes in Scrum, they remain valuable. For example:

• they support the Team by respecting the rules and spirit of Scrum
• they help remove impediments that the Team and Product Owner identify
• they make their expertise and experience available