Product Increment
At the end of every Sprint the team should have delivered a production quality increment of the system.
The Product Increment is what is
demonstrated to the users and stakeholders - working software rather than mock-ups, documents or hand waving.
One of the challenges that the team face is getting all the code built in a Sprint tested and bug
fixed before the Sprint Review. The key to achieving this goal is to ensure that the team
breakdown the Product Increment and attack small grains of functionality that cycle quickly
from design through to test.
When the Product Owner is satisfied that sufficient completed functionality at the desired level of quality
has been incrementally delivered through one or more Sprints, they can ask the team to Release the software.
This Release will more than likely require some effort to achieve and this takes place in a Release Sprint
Watch Ken Schwaber discuss what "Done" means.