NRI - Non Resident Indian:
A citizen of India (holding a valid passport issued by Govt. of India) and temporarily residing in the country of his/her present residence.
PIO - Person of Indian Origin:
Person of Indian Origin means a citizen of any country other than Bangladesh or Pakistan, if
- He at any time held Indian passport; or
- He or either of his parents or grandparents was a citizen of India by virtue of the Constitution of India or the Citizenship Act, 1955 (57 of 1955); or
- The person is a spouse of an Indian citizen or a person referred to in above two sub-clauses
Foreign national:
A citizen of a foreign country based in India.