What are the difference between guppy and fancy guppy?

there is not much difference but it is actually not called a fancy guppy its called a fancy tailed guppies because they have beautiful tails but beware if you have a male and female guppy or fancy tail guppy in the same tank the female will get pregnant and after the babies are born you must separate them or most of the babies will be eaten but beware the babies you can hardly see.