What is the difference between "SDN Platform" and "SDN Controller Platform"? These two indicate the same things? Could someone please explain this to me?
There is not much literal difference between these terms, and usually they are referred interchangeably. SDN Controller Platform is actually the controller software that takes care of entire network manageability.
The controller is said as a platform, as this gives the programmer the flexibility to add specific modules (for e.g., a routing module which takes care of routing only multicast packets using some very different routing algorithm) and run them on the controller. A controller when used without any specific modules, essentially sends all packets to everywhere (well, it depends on the controller implementation also). The controller is a platform where you are expected to do stuff and make your network behave the way you want.
And sometimes SDN Platform is used for SDN Infrastructure which includes topology, switches, one or more controllers and so on. Essentially describing the whole network infrastructure.
What you need to know is SDN components, like controller, switches, protocols etc.