Brahmanism was an early religion in the Indian subcontinent. It was based on Vedic writing and is considered to be the precursor religion of Hinduism. In Aryan society, there were different gods. Of those, Brahman was regarded as the most important one. Brahman was supported by Siva, the god of destruction, and Vishnu, the god of maintenance.
Brahmanism insisted on sacrifice to the gods. To conduct religious rituals correctly, there played an important role of priest, called Brahmans. If Aryans did not perform these rites, they would suffer from natural disasters such as floods, famine, etc. The Aryans paid the Brahmans to make these sacrifices and to conduct rituals. Thus, Brahmans were considered to be the highest caste of Aryan society. Over time, Brahmans made the sacrifices and rituals more and more complicated with stricter rules. They also propagate the idea of an afterlife.
This religion was born when the Aryan society was classified into different castes. Later on, Brahmanism was blended with the ideas of people already living in the Indus Valley, setting the foundation for the appearance of Hinduism.