Revisions is an easy way to create a backup copy of the work you are doing in the event you want to revert to a previous version. You can enable revisions for each page you create, or it can be incorporated as part of a Content Type.
Important Notes:
To access Revisions, click on the Revision information tab and check theĀ Create new revision. Be sure to enter a message to indicate how your changes affect the page. If this was built in as part of your Content Type, the checkbox will already be checked.