What is the Cold War and where did it take place?

The Cold War was a unique kind of war fought between Communist and Free World ideologies from 1945 to 1989. In some places it involved espionage. In some places it involved diplomacy and propaganda. And in some places like Vietnam, Korea, and Afghanistan it involved real war. The principal opponents were the US and USSR, but Great Britain, France and China were heavily involved too, and nearly every part of the world was involved in the Cold War to some degree. In basic terms, the opponents could not fight without starting another world war, so they found other ways to fight, and a balance was preserved.