Although FDI and FPI are similar in that they both originate from foreign investors, there are some very fundamental differences between the two.
The first difference arises in the degree of control exercised by the foreign investor. FDI investors typically take controlling positions in domestic firms or joint ventures, and are actively involved in their management. FPI investors, on the other hand, are generally passive investors who are not actively involved in the day-to-day operations and strategic plans of domestic companies, even if they have a controlling interest in them.
The second difference is that FDI investors perforce have to take a long-term approach to their investments, since it can take years from the planning stage to project implementation. On the other hand, FPI investors may profess to be in for the long haul but often have a much shorter investment horizon, especially when the local economy encounters some turbulence.
Which brings us to the final point. FDI investors cannot easily liquidate their assets and depart from a nation, since such assets may be very large and quite illiquid. FPI investors have an advantage here in that they can exit a nation literally with a few mouse clicks, as financial assets are highly liquid and widely traded.