Teams

In an Agile environment, resource management concepts--demand, velocity, commitment, and acceptance--are focused more on teams than on individuals. An Agile team is defined as "all of the team members who commit to all of the work required to complete a single story during a single sprint, including all tasks and dependencies that are related to that story." A team should only commit to working on stories that have a high priority and a high business value. And a team should use its velocity to determine how many stories to which it can commit in an upcoming sprint.

A sprint assignment is the process of moving a story into a sprint backlog from a release backlog or a team backlog.
A team assignment is the process of moving a story into a team backlog from a release backlog.

Teams frequently commit to more than one story per sprint, but it is important to understand that the effort required to complete the work required by a single story (including all of its related tasks and dependencies) is done in a single sprint by a single Agile team. Some assignments (like tasks) are identified before the sprint begins, while others (like defects and impediments) are discovered during the sprint. Assignments, once completed, are submitted to the team (for review) and to the product owner (for acceptance).

An Agile team is supposed to be small. This is by design. Good Agile teams share many of the following traits:

Have 7 or fewer team members
Are self-organizing
Have complimentary skills
Have collective knowledge
Work well together
Are cross-functional
Are co-located (as much as possible)
Frequently stay together in subsequent sprints

At a minimum, the relationships between product owners, product backlogs, and teams is 1:1 (meaning there is a single product owner who manages a single product backlog; the single product owner assigns a work item from the single product backlog to a single Agile team. There can, of course, be many more combinations than that.