A flag of convenience register is a national register offering registration to a merchant ship not owned in the flag state. The major flags of convenience (FOC) attract ships to their registers by virtue of low fees, low or nonexistent taxation of profits, and liberal manning requirements. True FOC registers are characterized by having relatively few of the registered ships actually owned in the flag state. Thus, while virtually any flag can be used for ships under a given set of circumstances, an FOC register is one where the majority of the merchant fleet is owned abroad. It is also referred to as an open register.

A flag state is the nation in which a ship is registered and which holds legal jurisdiction over operation of the ship, whether at home or abroad. Maritime legislation of the flag state determines how a ship is crewed and taxed and whether a foreign-owned ship may be placed on the register.

An internal register is a register of ships maintained as a subset of a national register. Ships on the internal register fly the national flag and have that nationality but are subject to a separate set of maritime rules from those on the main national register. These differences usually include lower taxation of profits, use of foreign nationals as crewmembers, and, usually, ownership outside the flag state (when it functions as an FOC register). The Norwegian International Ship Register and Danish International Ship Register are the most notable examples of an internal register. Both have been instrumental in stemming flight from the national flag to flags of convenience and in attracting foreign-owned ships to the Norwegian and Danish flags.

A merchant ship is a vessel that carries goods against payment of freight; it is commonly used to denote any nonmilitary ship but accurately restricted to commercial vessels only.

A register is the record of a ship's ownership and nationality as listed with the maritime authorities of a country; also, it is the compendium of such individual ships' registrations. Registration of a ship provides it with a nationality and makes it subject to the laws of the country in which registered (the flag state) regardless of the nationality of the ship's ultimate owner.

Military This category includes the entries dealing with a country's military structure, manpower, and expenditures.

Military branches This entry lists the names of the ground, naval, air, marine, and other defense or security forces.

Military expenditures - dollar figure This entry gives current military expenditures in US dollars; the figure is calculated by multiplying the estimated defense spending in percentage terms by the gross domestic product (GDP) calculated on an exchange rate basis not purchasing power parity (PPP) terms. However, in the case of Russia, estimates of military expenditures have been made using PPP. Dollar figures for military expenditures should be treated with caution because of different price patterns and accounting methods among nations, as well as wide variations in the strength of their currencies.

Military expenditures - percent of GDP This entry gives current military expenditures as an estimated percent of gross domestic product (GDP).

Military manpower - availability This entry gives the total numbers of males and females age 15-49 and assumes that every individual is fit to serve.