Mortgage/Refinancing question

This guy I know was talking about refinancing his mortgage the other day. Currently, he has a 30 year mortgage (which, I believe, is fixed rate and he is in year 3) but he said that once he refinances he will pay it off in 12 years. The only thing that even remotely makes this possible to me is paying the same mortgage note twice a month instead of once. But I'm fairly ignorant in this field so I don't know what the options are. Am I right with my assumption and is this beneficial? I didn't really want to ask him any questions for fear of sparking further conversation.