What is Sprint (in Scrum Methodology)?

Sprint is a cycle of agile based software development which is 3-4 week long time period. One thing to remember that Sprint is a consistent duration, so it should not happened that 1^st sprint is 3 week long and 2^nd sprint is 4 week long. How long should be the sprint must be decided by the sprint team (sprint team = Scrum Master + Product owner + feature team).

After completion of each sprint feature team delivers a shippable product, which must be a working product.

Each sprint is a set of tasks which together makes some feature/product, and these set of tasks are highly prioritize tasks created by Product Owner. Each sprint gives a tangible progress of development. Every sprint starts with Sprint planning meeting, and ends with sprint review meeting. One more meeting called Sprint retrospective meeting at end of each sprint is getting placed to understand the process changes required.