The Soviet Union was a large country in the middle of Europe that existed for many years after World War II. It was ruled by communist leaders. During this time, the Soviet Union wanted to control a lot of other countries and create an alliance of communist countries. This was known as the Soviet Union's foreign policy.
In order to make sure other countries agreed with their foreign policy, the Soviet Union sometimes sent troops, weapons, or money to other countries that agreed with their policies. They also sometimes set up governments in other countries, and made sure those governments followed their rules. This action was known as foreign intervention, and it was done so the Soviet Union could maintain control over those countries.
Sometimes other countries didn't like this, and it caused problems between countries, or even wars. Foreign interventions by the Soviet Union caused tension in the world, and it didn't always end well.