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 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.