Mormons believe their god was once a man and was ‘exalted’ through what they call ‘eternal progression’ into a god. They claim that by being a good Mormon, popping out a bunch of Mormonlings, tithing to the church, not asking any hard questions, wearing your magic underwear, and, I don’t know, fucking a magic hat or something, you too can become a god!

My wife is an ex-Mormon, she explains it better.