1. The term polarity refers to the world that was divided between two power blocs.
2. It was the period between 1945 and 1991.
3. The two power blocs are Communist power block under USSR and democratic Capitalist power bloc under USA. This, situation is called as bipolarity.
4. But in the year 1991 USSR was disintegrated and Russia was no more a super power.
5. From 1991 the world became unipolar i.e., one super power, America.
6. These are the different terms of bipolarity and unipolarity.