Raja means "royal," so Raja Yoga means literally Royal Yoga. It concerns itself more with the development of the mind than of the body, although the asanas (body positions) of Hatha Yoga are one of eight parts of Raja Yoga.
Raja Yoga is also sometimes called Ashtanga Yoga, and refers to the "Eight Limbs" (Ashtanga) of the yogic system first described in detail in the Sage Patanjali's Yoga Sutras more than a thousand years ago.
The Eight Limbs or Ashtanga
Put into the simplest and most inadequate terms — and in English to boot — here are my capsule descriptions of the Eight Limbs of the Yogic Tree. They are considered to be sequential, in that the first limbs deal with behavior and control of actions and the body, and later limbs deal with successively more abstract and spiritual training programs for the mind.
The first involved adhering to a righteous code of conduct. No hurting, lying, stealing.
The second is about commitment, mostly to the practice of yoga (and to one's religion).
The third involves learning the asanas or postures — this is the basis of most modern Hatha Yoga.
The fourth is about breath control, called pranayama, which means literally control of the life energy.
This is where the harmonica really starts to come into it!
The fifth is about bringing one's awareness inside, away from the five external senses.
The sixth — called Dharana — involves mental concentration, sometimes called "one pointedness." To me, this is the true purpose and practice of meditation.
The seventh — Dhyana — is perhaps a deeper form of Dharana, in which the person doing the one-pointedness meditation is no longer aware of the self. Only the mindfulness and the object of mindfulness seems to exist. When I am freely improvising, my goal is to be aware only of the music, with no thought for the situation or the person (me) who is playing, as I'm doing in the picture here, at B.B. King's Club on Beale Street in Memphis a few years ago...
The eight and last step is called Samadhi. In this step, the ego/individual self of the person is said to dissolve, leading to the state of non-dualism (if only for a few seconds). These last three limbs are, in my opinion, part of Jnana Yoga, and I attempt to discuss them further on that page of this site.