Nokia 6126 / 6131 / 6133

I still own my Nokia 6126 and it seems to be working now. I went and performed a master reset on the device and it seems to have cleared up the problems that I was having with the external display turning white and the phone freezing, which it has only done once. My question is this. What exactly does a master reset do in all cell phones to clear up problems, like the ones I was having? Does the master reset prevent any further problems from occuring in the future?