Everyone 
          knows the role of karma in day to day life as well as in spiritual field. 
          There are many ways to define karma. I will try to define it in a more 
          scientific way. There are three things 1. KARTA 2.KRIYA 3. KARMA. 
          KARTA = the person who performs any work. 
          KRIYA = the technique of work performed. 
          KARMA = karta + kriya (action). 
        It 
          means that a person doing any act is called KARMA. 
          We will try to understand karma in another way. A KARTA can be any living 
          or nonliving being eg. the sun, the earth, animals etc. are also doing 
          their KARMA like a human. They act according to their nature. This is 
          known as KRIYA. When there is ego or self-involvement in that act(KRIYA) 
          of the concerned individual, then it is changed into KARMA otherwise 
          it is only KRIYA. 
          If an individual feels that he is performing some act than it is known 
          as KARMA otherwise it is the act only. In other words we will say that 
          when person feels that he is doing some work then it is karma otherwise 
          it is NISHKARMA ( NISHKAM KARMA). 
          For a yogic practitioner it is very essential to understand the theory 
          of karma. In spiritual or yogic exercise we will always try to achieve 
          the goal of nishkam karma. Because it is the nishkam karma only which 
          can prevent from taking rebirths. 
          I have tried to explain this subject in yoga way. The practitioner should 
          understand that there are many methods to describe any subject. The 
          subject of karma according to SHRI MADBHAGWAD GEETA has been explained 
          in three divisions. They are 1. Karma 2 Akarma (prohibited acts for 
          a yogi) 3. Nishkarma (nishkam). 
          To achieve the goal of nishkam stage we have to pass through three main 
          stages. 1. Early stage 2 Middle stage 3 Final stage. 
          Early stage Learning stage (practice of yoga in starting). 
          Middle stage Advanced stage ( when practitioner has visualized internal 
          light etc). 
          Final stage In this stage the practitioner has completed all his exercises 
          but has not realized his soul. It is further subdivided in 1.Matured 
          samskar and 2. Superannuation or free from birth and rebirths. 
          Matured samskar means that the yogi is fit to realize his soul but he 
          does not know the way or yogic kriya by which he will be able to merge 
          himself in the God. 
          Superannuation is the final target for a yogi. By achieving this stage 
          he has completed his duties or has merged himself in God or has become 
          a self realized man or a perfect yogi etc. 
        HOW 
          IT HAPPENS
          Every act performed by a person results in sound, light and heat. These 
          three things are responsible for internal changes in the yogi or every 
          individual. We should carefully notice the acts of all animals eg. horse, 
          elephant, snake, goat etc. Like human beings animals also perform yogic 
          exercises and they also achieve their target. The God has given rights 
          to all his creatures for self-realization or merger in Him. 
          The inner darkness of our consciousness is slowly and surely changed 
          to light or realization of self by heating (burning of bad samskars 
          of previous births) and listening to the divine sound which purifies 
          the inner consciousness of the person making him eligible for the knowledge 
          of the Nature or God. 
          I would like to conclude by saying that yogic exercise is a scientific 
          process by which any individual can achieve his /her target by performing 
          correct exercises (kriyas) otherwise there are chances of getting into 
          more darkness in the form of confusion, illness, disrespect to the God 
          or Guru etc. If it happens it will be very unfortunate because there 
          is no remedy for it even if many births are taken. So please try to 
          understand that you have to choose a perfect master so that he can teach 
          you the purest form of yogic exercises. 
          Note: - samskars related with yoga have been discussed here only. 
        References:- 
          
          1. Shiv Maha Puran. 
          2. Shree Batuk Bhairava Upasana ch.124. Book published by Shree Venkateshwar 
          Press Mumbai-4. 
          3. Bhairava Sarvasva. Book published by Peetambara Peeth Sanskrit Parishad, 
          Datiya(M.P.). 
          4. Beej Yoga by Dr. Jal Singh. 
          5. Samskar Vigyan by Dr. Jal Singh.