Dharma :
Dharma is the principal of good way of life. These are the duties to oneself, the family and society.

Rita :
Rita is the principal that god preserve the harmony of the universe.

Karma :
Karma is the law of nature that contains the consequences of ones deeds. Karma is the result of all the deeds and non-deeds. When death will come, atman will go but karma will last. This karma will determine the future existence of the atman.