Well a hacker understands the fine points of a program/programming (we are talking bout computer hacker here).
Now its upto that person whether he wants to use his knowledge to harass people or to help.
he can identify bugs and weak links in a program and can then either inform the team in charge of that program to make a patch or he can post it on net and let other exploit that bug and ......
Yeah of course hacking and cracking are diffrenet. You bypass the authentication from the exe file, its called cracking. You force into someone elses pc finding a vulnerability, thats hacking.
You get to know a vulnerability in a program and use that info/program just to harass people thats called being a lamer, 'scriptkiddie' actually. :bleh: