The idea of dharma is a central belief of Hinduism. Its meaning cannot be easily described or translated. Like karma, it is a fundamental concept.
The essence of Dharma is duty, but it is more. It is a universal principle as well as a personal principle. Hindu scripture says:
Dharma is truth.
It is said that
one who speaks truth
and one who speaks dharma
Bhridaranyaka Upanishad 1.4.14
Dharma embraces family life, social life and spiritual life. It is the guideline known as Sanatana Dharma meaning Eternal Law or Eternal Order which actually defines Hinduism.
See On Hinduism by Irina Gajjar.