Why do we use it?

Rato Machindranath Jatra (Nepali: रातो मच्छिन्द्रनाथको रथयात्रा; Newar: बुंग द्यः जात्रा,Buṅga Dyaḥ Jātrā) is a chariot festival which is held in Lalitpur, Nepal. It is one of the greatest religious events in the city and the longest chariot festival celebrated in the country.

Buṅga Dyaḥ is also known as Raktalokitesvara, Karunamaya, and Rāto Machhindranāth and is revered as the god of rain and the giver of grains.[1][2] The name Rato Machhindranath means Red Machhendranath in reference to the color of the deity's image.[3] The chariot festival is held according to the lunar calendar, so the date is changeable. It begins on the 4th day of the bright fortnight of Bachhalā, the seventh month in the lunar Nepal Sambat calendar.