Information on breeding betta fish?

Hi I am wanting to get more information on breeding Betta fish. I am wondering about the whole Styrofoam cup thing? Ive seen people put them in the tank and its for the male to build his nest underneath it but ive also seen people just put a piece of Styrofoam in the tank? I don't understand this part and cant find any information on it. please let me know anything I need to know about breeding these fish. Thanks