Frizzle is a gene found in a few different breeds of chickens that make curly feathers (so to speak), I do believe they are trying to establish a frizzle as an actual breed in itself though. A sizzle is a cross between a frizzle and a silkie. It's pretty much just a silkie that carries the frizzle gene. If you breed 2 frizzle gene chickens together you end up with a frazzle, which looks pretty cute but their feathers are usually very brittle due to the double gene which is why they recommend breeding smooth feathered to curly.