The Islamic Republic of Pakistan is a country located in South Asia. It is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast.
Pakistan was created out of British India in 1948 as a Muslim state. Originally consisting of two parts - East Pakistan and West Pakistan, 900 miles apart - East Pakistan revolted in the early 1970s with the help of India and is now known as Bangladesh.
Most of Harry Turtledove's works are set, or have a POD, before 1948. Thus, the Pakistan of OTL rarely exists, and is usually still part of India.