What are thin-core and fat-core processors
Thin-core is a simple processing unit, slower with less registers, for example GPU core or small, low-energy core.
Fat-core is full-fledged CPU core. The mobile version of CPU is still fat-core

From article:  


  The IBM Blue Gene/P supercomputer (1 Pflop) is an example of a contemporary large-scale system design (294,912 processors) based on a many-thin (850 MHz, 1 Gbyte) processing-core approach.