This folder contains the iTunes backups of your devices. There should be a folder for each device with a long gibberish name. Do not mess with these folders in Finder.
You can manage this from inside iTunes. Go to the below screen in iTunes prefs and you will see an entry for each iDevice you are backing up to iTunes. You may have old devices in there from previous iPhones or iPads you can remove from the list. You do want to keep your current device in the list for iTunes backup though.
