Classical yoga under Patanjali has 8 different "limbs" of yoga. The first "limb" is the Yamas or social contracts. The second "limb" are the Niyamas or contracts with oneself. The third "limb" is Asana or yoga poses, there are hundreds! The fourth "limb" is Pranayama or breath. The fifth "limb" is Pratyahara or turning inward! The sixth "limb" is Dharana or concentration. The seventh limb is Dhyana or meditation. The eighth limb is Samadhi or awakening.
Awakening? Self realization? The simplest explanation for samadhi I have found is from BKS Iyengar: "Samadhi is an experience where the existence of 'I' disappears. Explanation can only come through the presence of 'I', so samadhi cannot be explained."
How great is that?!
I was going to stop right there but I have some more to add... Classical yoga breaks the universe into two parts: matter and spirit!