Custom of Jauhar in Rajasthan :

Jauhar, sometimes spelled Jowhar or Juhar, is the act of mass self-immolation by women in parts of the Indian subcontinent, to avoid capture, enslavement and rape by any foreign invaders, when facing certain defeat during a war. Some reports of jauhar mention women committing self-immolation along with their children.This practice was historically observed in northwest regions of India, with most famous Jauhars in recorded history occurring during wars between Hindu Rajput kingdoms in Rajasthan and the Muslim armies. 

The term jauhar sometimes connotes with both jauhar-immolation and saka ritual. During the Jauhar, Rajput women committed suicide with their children and valuables in massive fire, to avoid capture and abuse in the face of inescapable military defeat and capture. Simultaneously or thereafter, the men would ritually march to the battlefield expecting certain death, which in the regional tradition is called saka.

Jauhar by Hindu kingdoms has been documented by Islamic historians of the Delhi Sultanate, and the Mughal Empire.Among the oft cited example of jauhar has been the mass suicide committed in 1303 CE by the women of Chittorgarh fort in Rajasthan, faced with invading army of Khalji dynasty of the Delhi Sultanate.The jauhar phenomenon was also observed in other parts of India, such as in the Kampili kingdom of northern Karnataka when it fell in 1327 to Delhi Sultanate armies.

Etymology :

The word jauhar is connected to Sanskrit jatugr?ha "house plastered with lac and other combustible materials for burning people alive in".[19] It has also been wrongly interpreted to have been derived from the Persian gauhar which refers to "gem, worth, virtue". This confusion Hawley states rose from the fact that jivhar and jauhar were written in the same manner with the same letter used to denote v and u. Thus its meaning also came to wrongly denote the meaning of jauhar.

 Main occurance :

Sindh: After the first Arab invader Muhammad Bin Qasim defeated King Dahir, his wife continued to hold the defense till she could and finally committed Jauhar.
Gwalior: After the attack of the Delhi Sultan Iltutmish.
Ranthambore: After the attack of Delhi Sultan Alauddin Khilji (immensely popular for marrying the wives of kings conquered).
Chittor: Invaded thrice.
Jaisalmer: Invaded twice.
Chanderi: After Babur’s attack.
Raisen (Madhya Pradesh): Sacked Thrice.
Bundelkhand: When Aurangzeb attacked the fort, Jauhar was committed. However, those who were unable to complete the ritual were captured and forced into the harem. 

The possessive Rajput husbands, who were intent on performing Saka till death, could not bear that their women marry other men after their death in Saka, and that too Mleecha men whom they deemed barbaric, uncivilized and inferior to Rajputs. As a result, to prevent this, and to satisfy their own possessiveness towards their wives, they killed their females by throwing them into fire, even if their females were not willing to die. After ensuring that their females would not be able to enjoy life with new, handsome, Muslim husbands (after their death), they happily gave up their own life in Saka, and then, through their bards and descendants, ensured that these victims of “honor killings” would be hailed as “Maha Satis”.

Whenever the defending Hindu armies faced an imminent defeat and ran out of supplies, they used to take a brave decision. Records indicate that Jauhar took place at night. Brahmin priests attended this practice, chanting Vedic texts. As the Brahmin priests chanted, women threw themselves and their children into a fire while wearing their wedding dresses. They jumped into the fire to make sure that a Muslim invader could not even rape their dead bodies.

The next morning, men performed the Saka ritual. They bathed, put on saffron, placed a tulsi leaf in their mouths, and marked their foreheads with the ashes of their wives and children. The men then rode off into battle with the enemy. The men did not allow themselves to be taken alive either. This was called as Saka.

Difference between Sati and Jauhar :

The term Sati (also spelled as “Sauttee” in English) literally means pious bride. That so-called piousness was assigned to those brides due to their great ability to serve all the whims and demands of their husbands to make his life as happy and luxurious as possible. Later the same term “Sati” started to be used to refer basically “sati-daha” or burning of such sati, who “willingly” sacrifice their lives after her husband’s death.

The main, probably the only, real world difference between Sati and Jauhar is:
Sati is not any mass murder or mass suicide, but more of a single act of a crime. On the other hand, Jauhar is more of a community or mass murder or mass suicide, depending on one’s view point.

The other difference would be- sati is more common among almost all Hindu communities in Indian subcontinent, that include Nepal as well. It’s widely used among priest class of Brahmans in Bengal, who had nothing to do with war and mostly involved in religious preaching and worship. They used to marry many wives till they become too old (even to marry) and die soon after- leaving all those wives (many would be very young in their teens).

Jauhar is more appropriate for women from Khatriya or warrior or king class families in few states in western India like Rajasthan.