The Dharma Sastras contain treatises on ethical and social philosophy compiled to deal systematically with the proper conduct of life and describe social, ethical and religious obligations.

The Sruti and the Smriti are the two authoritative sources of Hinduism.

Sruti literally means what is heard, and Smriti means what is remembered. They contain the ancient sacred law codes of the Hindus.

The Smritis or Dharma sastras explain and develop dharma.

There are eighteen main Smritis. The most important are those of Manu, Yajnavalkya and Parasara.
The other fifteen are those of Vishnu, Daksha, Samvarta, Vyasa, Harita, Satatapa, Vasishtha, Yama, Apastamba, Gautama, Devala, Sankha-Likhita, Usana, Atri and Saunaka.

The laws of Manu are intended for the Satya Yuga. Those of Yajnavalkya are for the Treta Yuga.
The laws of Sankha and Likhita are for the Dvapara Yuga and those of Parasara are for the Kali Yuga.