Course versioning is a reporting tool that allows you to label and track changes to your courses. When editing any course, select SAVE AS NEW VERSION on the right sidebar and a new window will appear. This allows you to specify a version number, as well as enter any notes for this particular version.
Saving a new version of your course does not preserve previous versions, and Absorb does not feature any restore/rollback functionality to these previous versions. Course versioning is basic form t tool that allows admins to remind themselves (or others) of any changes they have made to the course, as well as the dates/times the changes took place.