The scrum development team is a term that is used to encompass all the technical team members within the scrum process, including testers, designers, and ops engineers in addition to developers.
Scrum teams control their own destiny and self-organizes around their work. Agile teams use 'pull' models, this means that the team pulls a certain amount of work from he backlog and commits to completing within the sprint being planned.This model has been shown to be effective in maintaining quality and as a long term perspective, ensuring optimum performance of the team.
As mentioned above, the scrum team is the primary source of decision making when planning a sprint. With the help of historical velocity as a guide, the team forecasts how much work can be delivered within the sprint. Keeping the iteration length fixed gives the development team important feedback on their estimation and delivery process, making the team's forecasts grow in accuracy over time.
The scrum team is, by definition, a tight knit one and they are the champions for sustainable development practices. The most effective scrum teams are close (each member adoption a 'we' attitude, co-located, and usually comprise of 5 to 7 members. The members of the scrum team use their different skill sets to help each other so that, as a team, they successfully complete the sprint.