As you install, upgrade, and uninstall software into your system, configuration snapshots are kept in a history. Reverting to a previous configuration allows you to back out of the results of an unsuccessful install, upgrade, or uninstall. To revert to a saved configuration:
Installation Details... to open a dialog showing pages that provide more detail about your installation. 
Installation Details
Updating the installation
Installing new software
Updating software using the Available Updates wizard
Uninstalling software