The term Hindu Social Classes refers to the system of castes in India. Castes are social groups that are determined by birth and are hereditary, meaning that one's caste is determined by their parents. The four main castes are Brahmin, Kshatriya, Vaishya, and Shudra. Each caste has its own set of duties and responsibilities, and members of each caste are expected to marry within their own caste.