The policy of containment was the foreign policy approach that the US adopted after WWII, during the so-called Cold War Era. It aimed to stop the expansion of the URSS influence and the spread of communism all over the world.
Through this policy, the US tried to influence non-communist nations to that they would side with them on this fight. Moreover, the US intervened on those countries that were being attracted by the URSS, siding with the local forces that aimed to impede the sucess of communism.
Therefore, the world was highly polarized and two blocs were formed: the Eastern bloc of communist countries leaded by the URSS and the Western bloc of capitalist countries headed by the US.