what does mean softfp. gcc related

Hi list, I confused by arm gcc flags In gcc user guide: -mfloat-abi=name `softfp' allows the generation of code using hardware floating-point instructions, but still uses the soft-float calling conventions. `hard' allows generation of floating-point instructions and uses FPU-specific calling conventions. eg: -mfpu=vfp -mfloat-abi=softfp what does this mean if arm support vfp instructions. what's the different between "-mfpu=vfp -mfloat-abi=softfp" and "-mfpu=vfp -mfloat-abi=hard". can someone give me a hand? Thanks Lei