Found some topic here when man asking about gpuvscpu. And someone wrote the right thing " Cpu and gpu are the waste of time because there are ASIC's on the scene"

Could someone explain fundamental difference between gpu and ASIC. I thought ASIC's are powerful gpu's specialized to mining bitoins.  For this reason ASICs are cheaper the gpu farm in $/hash 

Are there some conceptual difference between gpu and ASIC?