Oracle JDK7 itself is not hosted in the PPA because that's not allowed by the new Java license (which is also the reason why it has been removed from the official Ubuntu repositories); the package in the PPA automatically downloads (and installs) Oracle Java JDK 7 from its official website and installs it on your computer, just like the flashplugin-installer package does.

For more info, how to install, etc., see: http://www.webupd8.org/2012/01/install-oracle-java-jdk-7-in-ubuntu-via.html