A cohesive set of responsibilities that can be fulfilled by one or more people. The three Scrum roles are:

The fundamental unit of Scrum is a small team of people, a Scrum Team.
The Scrum Team consists of one Scrum Master, one Product Owner, and Developers. Within a Scrum Team, there are no sub-teams or hierarchies.
It is a cohesive unit of professionals focused on one objective at a time, the Product Goal.
Scrum Teams are cross-functional, meaning the members have all the skills necessary to create value each Sprint.
They are also self-managing, meaning they internally decide who does what, when, and how.

Self-organized teams choose the best way to do their work, rather than being led by others outside the team. - Scrum guide 2017.
Self-managed, which means they internally decide who does what, when, and how.
Traditional, self-managing and self- designing/organising teams, self-governing (Hackman, The design of work teams, 1987, p. 334).
Overall, we've found that smaller teams communicate better and are more productive.

Developers are the people in the Scrum Team that are committed to creating any aspect of a usable Increment each Sprint.
The specific skills needed by the Developers are often broad and will vary with the domain of work.
● Creating a plan for the Sprint, the Sprint Backlog
● Instilling quality by adhering to a Definition of Done
● Adapting their plan each day toward the Sprint Goal
● Holding each other accountable as professionals
