Rooted in religion and based on a division of labor, the caste system, among other things, dictates the type of occupations a person can pursue and the social interactions that she may have. Castes are an aspect of Hindu religion. Other religions in India do not follow this system.
-istan is a suffix in the Persian language (Farsi), denoting a place. Thus, Pakistan means place of the pure (pak=pure). It does not just refer to geographical areas, as in bimarestan=place of the sick=hospital. The suffix is widespread in Eurasia because of Persian influence (the Mughals of India for example used Farsi).
Pakistan is bordered by India on the east, the Arabian Sea on the south, Iran on the southwest, and Afghanistan on the west and north; in the northeast is the disputed territory (with India) of Kashmir, of which the part occupied by Pakistan borders on China. Islamabad is the capital and Karachi is the largest city.