The YZF in Yamaha stands for Yamaha Racing Factory. It is an acronym used to identify Yamaha's racing bikes and other high performance vehicles. The YZF line of bikes from Yamaha have been some of the most powerful and successful racing bikes in the world. They have consistently been at the top of the list for fastest and most reliable bikes in the world. The YZF line has been used by some of the most famous racers, including Valentino Rossi and Marc Marquez.