The Overseas Citizenship of India (OCI) is an immigration status permitting a foreign citizen of Indian origin to live and work in the Republic of India indefinitely.
A Person of Indian Origin (PIO) means a foreign citizen (except a national of Pakistan, Afghanistan, Bangladesh, China, Iran, Bhutan, Sri Lanka and/or Nepal), who: at any time held an Indian passport.
All foreigners (including foreigners of Indian origin) visiting India on long term (more than 180 days) Student Visa, Medical Visa, Research Visa and Employment Visa are required to get themselves registered with the Foreigners Regional Registration Officer