The word karma is derived from Sanskrit word ‘kri’ which means to do; or ‘action’(karma) . Karma yoga is purifying the mind by means of work. Now if any work is done, good or bad, it must be produce as a result a good or bad effect; no power can stay it , once the cause is present. Therefore good action producing good karma, and bad actions, bad karma. Karma belongs only to the body or the mind, never to the Ātman (self) ; only it can cast a veil before the Ātman.
The veil cast by bad karma is ignorance. Good karma has the power to strengthen the moral powers. And thus it creates non-attachments; it destroys the tendency towards bad karma and thereby purify the mind. But if the work is done with the intention of enjoyment, it then produces only that very enjoyment and does not purify the mind or chitta. Therefore all work should be done without any desire to enjoy the fruit thereof. All fear and all desire to enjoy here must be banished for ever by the Karma yogi. Moreover, this karma without desire of return will destroy the selfishness, which is the root of all bondage. The watchword of the karma yogi is “not I, but Thou”.