A protectorate usually refers to a country or territory that is govered and protected by a more powerful contry. The smaller is the protectorate and the larger would be the protector (though the second is less commonly used).
There are different degrees to which the protectorate is controlled, and sometimes it might not be controlled at all, just protected. Kozovo and Bosnia are often refered to as protectorates of NATO.
Puerto Rico is a protectorate of the US. Monaco is a protectorate of France. Many countries of the Brittish commonwealth used to be protectorates, such as Hong Kong (until 1997) and Kenya (until 1963).