Karma is derived from the Sanskrit word "Kri" to do , all action leads to Karma. In the four main paths of Yoga - Karma-Yoga, Bhakthi-Yoga, Jnana-Yoga and Raja-Yoga one thing that stands out in Karma-Yoga is that doing unselfish duty also leads to salvation. It is not necessarily the Sanyasi (or) the Jnani who unites with the divine, but the gruhastha can as well reach the same destination as long as the work is unselfish. The goal of mankind is knowledge and not pleasure and happiness as some people believe. Karma-Yoga is a system of ethics and religion intended to attain freedom through unselfishness and by good-work
One of the direct translation of Gita says " Actually, not even for a moment can one remain free of activity - including mental activity, both unconscious and subconscious. The energy within the body-mind organism will automatically produce actions according to the natural charecterisctics of the organism. Whenever the senses get in contact with an object by seeing or hearing, the brain produces an action in accordance with the natural charecterisctics. While we think we are "doing it or performing the action as a reaction to the event" it is in reality the natural characteristics and we need to be un-attached to the action, lest it gets into a vicious circle of "I did it" and triggers another event and action.