When the Soviet Union was around, they had an idea called a "state ideology." That means the leaders of the country wanted everyone to agree on certain ideas and ways of doing things.
Their state ideology had two main parts:
1. Communism - This is an idea that everyone should work together and share everything. This means no one person owns anything, and everyone helps each other out.
2. Marxism-Leninism - These are ideas from two guys named Marx and Lenin. They believed that the working class (the people who work to make money) were being treated unfairly by the rich people. They wanted to change society to help the working class have more power.
The Soviet Union's state ideology said that everyone should follow these ideas, and if they did, everyone would be happy and equal. They wanted everyone in the country to think the same way, and they even taught these ideas in schools.
However, not everyone agreed with this ideology, and some people thought it wasn't fair or successful. That led to disagreements and conflicts within the Soviet Union.