The "sphere of influence" was a type of imperialism
that stopped short of full colonial domination. Imperialist powers would agree among themselves to divide up subject territories, usually without the consent of the dominated peoples involved. Once a power secured recognition of a sphere of influence, it would be free to conduct trade and establish railroads and factories and the like without interference from the other powers. The concept of spheres of influence was first articulated at the Berlin Conference
Perhaps the most notable use of spheres of influence was in China, which was too big to be colonized outright. Instead, the European nations divided China into spheres of influence, where their traders could establish lucrative monopolies. If a French entrepreneur wanted to trade in the English sphere, he would have to secure England's permission, and vice versa.