Vishnu is the preserver and protecter of the universe. He is reincarnated when the world needs to be brought back into balance. It's thought that he has already been reincarnated nine times, and is going to come back for the end of the universe. He is represented as a human who is blue with four arms.
In Hinduism, sādhu means “good; good man, holy man”) denotes an ascetic, wandering monk. Although the vast majority of sādhus are yogīs, not all yogīs are sādhus. The sādhu is solely dedicated to achieving mokṣa (liberation), the fourth and final aśrama (stage of life), through meditation and contemplation of brahman.
Sahdus are people who have renounced the Caste System, social status, money, and authority and have a special place in Hindu society. They are considered superior to priests. They are credited with a lot of influence of Indian culture. They don't cut their hair or their beards ever. The Sadhu is buried in a sitting position, unlike most Hindus. Their burial grounds are considered sacred.