The name comes from the earthen pot with a spout (karwa, from the Sanskrit karaka) used in the puja, and chauth, meaning the fourth day. The karwa filled with water is offered during the puja and later used to offer water to the Moon. Parvati is worshipped as the ideal of steady devotion in marriage, and the Moon, which governs the mind in Vedic thought, is honoured as the witness of the vow.
Beyond the fast, Karwa Chauth is a festival of togetherness. Women dress in bridal or festive clothes, apply mehndi, gather in the evening to hear the katha and perform the puja together, and families exchange gifts between the woman's parents and her in-laws.
Today many couples observe the day as a shared commitment. Some husbands fast alongside their wives, and some unmarried women keep the fast for a good life partner. The practice is traditional and personal; there is no single correct way to observe it.
The best-known story is of Veeravati, the only sister of seven loving brothers. On her first Karwa Chauth after marriage she was fasting at her parents' home and grew faint with hunger and thirst. Unable to bear her distress, her brothers lit a fire or lamp behind a tree (in some versions using a sieve or mirror) so that it looked like the Moon had risen. Veeravati broke her fast, and soon received news that her husband had fallen gravely ill.
Realising what had happened, Veeravati was filled with remorse. She prayed to Parvati and kept the Chauth fasts of the following year with full devotion. Moved by her sincerity, the goddess blessed her and her husband was restored to health. The story is told at every Karwa Chauth gathering as a reminder of patience, faith and keeping one's word.