Yama : The word, yama, means “to harness” or “to restraint” These practices are related to disciplining the self on external or social levels. These are the methods of applying the behavioral codes of yoga on how the Yogi deals with the external world or the people in general. It relates to externally visible discipline or etiquette.
Niyama : Niyama is related to disciplining the self from within while keeping the connection with external realities with no attempt to deny them. It is the act of disciplining the emotions within, even if the external situation does not change. However, one should try to change the external difficulties, if it is logical and real.
Asana (posture or position) : Interestingly, asanas are closely related to yama and niyama. One can experience the ease of performing Asanas only when one follows the first two limbs of Yoga properly. Therefore, perfection of asanas are linked to proper harmony between Yamaand Niyama. This is the reason a real Yoga teacher does not push the student to stretch to his limits while performing Asanas but in contrast, the teacher asks the student to be alert and stretch only according to his capacity. It is called as, “sthiram sukham asanam,” which means stability and satisfaction while performing the asanas. In fact if one starts performing the asanas properly under the guidance of good teacher then the first two previous principles also become a requirement for yoga student. So following the first two limbs are important before performing the asanas, as it’s not possible for a disturbed person to even stand in one place, what to speak of performing any asanas.
Pranayama (balancing the vital energy) : When we see a person heavily panting in the start of an uphill trekking itself, we can easily deduce that the lungs of that person have not opened up clearly. Trekking is natural only when the lungs are open. So Breathing is very much important to one's movement and pranayama deals with this aspect. Those who breathes nicely, not only the brisk walking becomes possible for them but it also helps them in making clear decisions. It is also observed that a person who is confused or excited state, they experience the breathing troubles. Pranayama teaches to control the breath and learning pranayama enables practitioner to strike a proper balance in all aspects of life including physical levels, mental levels, speech, decision-making and in execution of his work.
Pratyahara : Pratyahara means to withdraw. The withdraw here does not refer to retiring.It actually refers to cultivating the ability of performing the action at one’s own will. To hold back the action when not required, and release them whenever required. It is the art of detached involvement.
Dharana : It is the art of focusing on one thing for very long time. Dharana from practical perspective is an ability to keep doing something for very long time.
Dhyana : The word dhyana means to contemplate or meditate. It requires one to sit down and have complete absorption on the object of meditation. Same dhyana can also be achieved when someone is deeply involved in some activity for long time with expertise, just like Arjuna was focused in the art of archery.
Samadhi : During Samadhi the action, the actor and the experience merges as one, when one is in absorbed reality. In other words we can say that, though the doer, the activity and the experience, are different to each other, but when the doer is completely involved in activity than all the three experience become one.