time machine

One option is to mount the Time Machine backup drive to your Mac's Desktop using the Finder app, and then drill-down to any of the backups to see what has been backed up. Note: The short answer is that all of your Mac's data is backed up.

Alternatively, there are a number of third-party apps that can be used for this purpose as well. One of these, is CharlesSoft's TimeTracker.

Time Machine backs up everything, it does backups hourly and only backs up the new or revised information. Perhaps you may want to click the link at the very top of this web page which provides more information about Time Machine.