Every time you save a Space, a new version is saved with all of your configurations. To access the version history, go to a Space and enter Edit Mode. Then, on the top right corner (next to the Publish button), click on the ᐧᐧᐧ menu. Then, select "Version History" from the menu.
The version history displays all versions that have been saved in the past along with information on who saved it and when. Additionally, if a version is currently published to one or more environment, you'll find that information here as well.
To restore a version, click "Restore Version". This action does not impact what is currently published. To publish the version, click "Publish" on the top left corner once you restore the version.