Hello, Vinay S.
This is not a simple question but I'll take a stab at starting to provide an answer, at least.
Where ThingWorx fits in the Navigate architecture is to provide a basis for the User Interface as seen through Navigate. Windchill itself has an expansive and sometimes overwhelming interface, in the sense that a lot of data is supplied and often more than is necessary for a particular use case.
What ThingWorx does is pull appropriate data from Windchill and then integrate that into display mashups that are more specific to particular tasks; i.e. it acts as a smart filtering mechanism. And once the data is pulled into ThingWorx other tools can be brought to bear on it; visualization via ThingWorx Studio and analysis via ThingWorx Analytics to name a couple.
Does this help at least starting to fill in the gaps?
-- Craig A.