Bipolarity
Bipolarity is a distribution of power in which two states have the majority of economic, military, and cultural influence internationally or regionally. Often, spheres of influence would develop. For example, in the Cold War, most Western and capitalist states would fall under the influence of the USA, while most Communist states would fall under the influence of the USSR. After this, the two powers will normally maneuver for the support of the unclaimed areas.
Read more about this topic: Polarity In International Relations