Hard reset VS defaults settings

Hi all ,

Can someone explain me what is the difference between a hard reset (to press on the switch in the camera ) and to reset the camera to defaults setting in the interface ?
It is the same things or not ?

I would like to understand this because i have updated my camera with a new firmware , and the camera was bugging ... with defaults settings in the camera interface problems was the same , with hard reset all is now ok !

thanks very much

BICK