What are the Release types available on the baseline release record?
During the release planning process, release managers define the type of the release (major, minor, and so on.), schedule of the release (planned start and end dates), required phase, phase tasks, and the scope.
https://www.servicenow.com/docs/bundle/xanadu-it-service-management/page/product/release-management/task/t_DefineARelease.html