Originally Posted by d3vski

OCI is a multi-purpose, multi-entry lifelong visa (basically Permanent Resident Status) given to people who are descendents (upto 2 generations) of those who are/were Indian Citizens. You can turn up tomorrow and live there forever!

Just checked my old 5 year visa, although the category is "X", the small print at the bottom of the visa clearly states:

Visa for tourist, non-extendable, change of purposes not allowed, not valid for protected, restricted and cantonment areas