After the Second World War ended in 1945, the world was left with two dominant superpowers: the United States (democratic, capitalist) and the Soviet Union (communist, authoritarian). Both had enormous armies. Both, by the early 1950s, had nuclear weapons capable of destroying entire cities. And they disagreed — fundamentally — about how the world should be organised.
This became the Cold War: a decades-long global confrontation where both sides competed for power, influence, and allies without ever directly fighting each other. "Cold" because the two superpowers themselves never exchanged a single shot.
Imagine two very large, very well-armed people staring at each other across a room. Both know that if one pulls a gun, the other will too, and both will get shot. So instead they spend their time trying to make friends with everyone else in the room, starting arguments between other people, showing off to make themselves look more impressive, and occasionally running to the same door to get there first. That's the Cold War. The guns (nuclear weapons) prevented direct conflict by making it suicidal for both sides. This is called Mutually Assured Destruction, or — appropriately — MAD.
How did they compete?
The US and USSR competed in almost every arena except direct war. They fought proxy wars — backing opposite sides in conflicts in Korea, Vietnam, Afghanistan, Angola, and elsewhere. They raced to be first in space (the Soviets launched Sputnik in 1957; the US landed on the Moon in 1969). They stockpiled weapons, funded intelligence operations, and tried to install friendly governments across the developing world.
What was the Iron Curtain?
After the war, the Soviet Union installed communist governments across Eastern Europe — East Germany, Poland, Czechoslovakia, Hungary, and others. A sharp division opened up between the democratic West and the communist East. Winston Churchill called it the Iron Curtain. Families were separated, travel was restricted, and the Berlin Wall (built in 1961) became the most literal symbol of the divide — a concrete barrier through the middle of a city.
How did it end?
In the 1980s, the Soviet economy was struggling badly — the cost of the arms race, failed central planning, and the war in Afghanistan were taking a severe toll. The Soviet leader Mikhail Gorbachev introduced reforms (glasnost — openness; perestroika — restructuring) that loosened the system's grip. In 1989, communist governments fell across Eastern Europe in rapid succession. The Berlin Wall came down in November 1989. In 1991, the Soviet Union itself dissolved. The Cold War was over.