Raja Yoga (lit. Royal Yoga) is the system of yoga outlined by Patanjali in his Yoga Sutras. It is also sometimes referred to as Ashtanga (eight-limbed) yoga because there are eight aspects to the path to which one must attend.
The eight limbs of yoga are so logical and easy to understand that virtually every teacher of yoga claims to be teaching them, which is true to one degree or another, because the eight limbs cover everything one can do in yoga. In this sense, they represent a complete road map, a blueprint and spiritual checklist of the various ways to open the human nervous system to divine experience.