Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Rawhide is the development version of Fedora which includes the latest upstream packages. At some point in the Fedora release schedule a fork (called branched release) is created to become the next stable Fedora and the rawhide version continues on its own.
As of today Fedora Rawhide contains packages that will be part of both Fedora 19 and Fedora 20. If you want to take a peek at the next Fedora version, Rawhide is what you need, but bare in mind though that it can be unstable so in the event of a system crash you should know what to do to recover it.