Just a question here ~ how the real money auction house actually working?

Because my friend do confuse me..he say that the money inside that bank account(such as paypal) can only use in blizzard..but cannot withdraw out in real life....

it is i have to own a bank account in order to do the RMAH?
And the money i can withdraw from that account and use it in real life? or it lock under blizzard..and the so call $$(not gold) in d3 only can use to purchase in game item? or i can refund it from my account (just like ATM)

Ok ~ Get it ~ thx for the info