The Sprint
A Sprint is a time-boxed period of time (quite often 30 sequential calendar days, or 20 working days) during which the Team works to turn the Product Backlog items it has selected into an increment of potentially shippable product functionality.
The iteration length of around a month is long enough to produce something of value and to production quality such that it is worth demonstrating to the Product Owner and stakeholders. Any longer and the Team will lose agility through the need for artefacts and documentation to support the development process.
The goal and activities for the Sprint are planned at the beginning of each Sprint in the Sprint Planning meeting.
Progress of the Sprint is tracked with the Sprint Backlog and Sprint Burndown chart.
Watch Ken Schwaber's guidance on the Sprint.

