A release sprint, often part of a project using agile management methodologies, incorporates activities, sometimes not related to creating product features, that the development team can't realistically complete within development sprints. To accommodate prerelease activities and help ensure that the release goes well, scrum teams often schedule a release sprint as the final sprint prior to releasing product to customers.
The release sprint should contain anything you need to do to move the working product to production. Sprint backlog items in a release sprint may include
Creating user documentation for the most recent version of the product
Performance testing, load testing, security testing, and any other checks to ensure the working software — or other product — will perform acceptably in production
Integrating the product with enterprise-wide systems, where testing may take days or weeks
Completing organizational or regulatory procedures that are mandatory prior to release
Preparing release notes — final notes about changes to the product
If your product is software, backlog items for the release sprint may also include
Preparing the deployment package, enabling all the code for the product features to move to production at one time
Deploying your code to the production environment