Traditional Indian society was built around a collection of endogamous groupings called jatis ("birth").
The group's ancestral occupation, over which each group had a monopoly, was used to arrange (and establish their social rank) these jatis.
The Doms are a jati whose ancestral employment was cremating corpses in old northern Indian culture.
They have a poor social position due to their frequent interaction with dead corpses, which are considered the most brutally filthy of all items.
Despite their low rank, some Doms are quite rich, notably those who oversee the cremation ghats in Benares, since a corpse cannot be burnt without their participation.
Any flat region on a river's bank is referred to as a ghat.
The majority of the time, ghats are used for bathing (snana), but in certain situations, they are also used to burn corpses so that the ashes may be thrown into the river to "cool" them ritually.
You may also want to read more about Hinduism here.
Be sure to check out my writings on religion here.