Andrew Michael Miller's Thought Backlog
Writer and working Agile professional. Author of Pancho's Fall.
All sprints come to an end. After a set period of time, the sprint will come to a close and the team will review the work done in the sprint, and then reflect on the things that went right and the things that went wrong in the sprint. A new sprint begins as soon as the current sprint ends. Every sprint should be able to produce something immediately usable.
In Scrum, it's important that developers communicate when they are working on stories. (Stories are the fully-broken down chunks of work that are put into the Sprint Backlog.) When a developer starts working on a story, they need to indicate in some way that they have assigned themselves that work, or else there is a risk that another developer might start working on the same story without knowing it's already being worked.