What does "Drain diffusion res squares, Source diffusion res squares, estimated operating region, thermal resistance, num of segments, and thermal capacitance" mean in analogLib's ntft?

I want to simulate analogLib's ntft at the cadence virtuoso.

By the way, I do not know What does  "Drain diffusion res squares, Source diffusion res squares, estimated operating region, thermal resistance,num of segments and thermal capacitance" mean in analogLib's ntft. (Please refer to Figure 1.)

                                                      Figure 1

Could you tell me What does  "Drain diffusion res squares, Source diffusion res squares, estimated operating region, thermal resistance, num of segments, and thermal capacitance" mean in analogLib's ntft?

Thank you 

yysunj