Hi masoomshaikh!
PPL did exist in the prior versions of Visual Studio but did not have all functionality we need for Casablanca. It obviously did not exist on Linux.
PPLX is a port of PPL to Visual Studio 2010, Visual Studio 2012, and also Linux. It is not needed for the new (soon-to-be released) version of the Visual Studio 2013, in which you can just use the "stock" PPL.
I hope that makes sense.
PPL did exist in the prior versions of Visual Studio but did not have all functionality we need for Casablanca. It obviously did not exist on Linux.
PPLX is a port of PPL to Visual Studio 2010, Visual Studio 2012, and also Linux. It is not needed for the new (soon-to-be released) version of the Visual Studio 2013, in which you can just use the "stock" PPL.
I hope that makes sense.