Samsara: the idea that after we die our soul will be reborn again in another body. Perhaps in an animal, perhaps as a human, perhaps as a god, but always in a regular cycle of deaths and resurrections.
Karma: means “action”, the idea that all actions have consequences, good or bad. Karma determines the conditions of the next life, just like our life is conditioned by our previous karma. There is no judgement or forgiveness, simply an impersonal, natural and eternal law operating in the universe. Those who do good will be reborn in better conditions while those who are evil will be reborn in worse conditions.
Dharma: means “right behaviour” or “duty”, the idea that we all have a social obligation. Each member of a specific caste has a particular set of responsibilities, a dharma. For example, among the Kshatriyas (the warrior caste), it was considered a sin to die in bed; dying in the battlefield was the highest honour they could aim for. In other words, dharma encouraged people of different social groups to perform their duties the best they could.
Moksha: means “liberation” or release. The eternal cycle of deaths and resurrection can be seen as a pointless repetition with no ultimate goal attached to it. Seeking permanent peace or freedom from suffering seems impossible, for sooner or later we will be reborn in worse circumstances. Moksha is the liberation from this never ending cycle of reincarnation, a way to escape this repetition. But what would it mean to escape from this cycle? What is it that awaits the soul that manages to be released from samsara? To answer this question we need to look into the concept of atman and Brahman.