What is the difference between buying a house and rent to own deal?

what is the difference between buying a house and rent to own deal. is that another way of getting a loan ..but at higher interest rate - the rent to own deal . In this case is the rent to own guy actually loaning me the amount to buy it . Please help me ..thanks
Sam
Update: THANK YOU all so much. I knew it might end up like , picking a rattlesnake !!!
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