Deploying a release performs the selected action (publish or unpublish) on the items of that release associated with a specific environment.
So, for instance, let’s assume that you have added five items to a release (3 for publishing and 2 for unpublishing). When you deploy this release, the three items added with the publish action will be published, and the two with the unpublish action will be unpublished, all at once.
To deploy a release, log in to your Contentstack account and follow these steps:

Note: You can update the release items to their latest versions before you deploy the release. Refer to our Update Release Items to their Latest Versions documentation for more information.
If you select Now, Contentstack will immediately deploy all the added items in the specified environment.

If you select Later, you need to specify the Date and Time at which the release should be deployed, along with your time zone.

Note: The deployment date cannot extend beyond 12 months when scheduling a release.
Note: Once you deploy a release in an environment, all the items within are locked. You can unlock the release and make the necessary changes.
To deploy the Release via API, refer to the Deploy a Release API request.