Does virgin mobile use sim cards?

I found out virgin mobile has the iPhone and for only $30 a month. But the iPhone costs $550-650. Could i just buy an iPhone from amazon or craiglist or something and then get a phone plan from virgin mobile? I really need to know if thats possible or else i'll have to start saving

Virgin Mobile uses CDMA. Which means no SIM cards. They don't have towers of their own, but they pay Verizon and Sprint (the 2 major CDMA providers) to use their towers. And no you cant do that