Okay, so imagine you and your friend got into a big fight and were really angry with each other. But then, you both decided to say sorry and make up. That's kinda like what happened with the Soviet Union and Lithuania.
A long time ago, Lithuania used to be a big country all on its own. But then the Soviet Union came along and took over, which made a lot of people in Lithuania really unhappy. They didn't like being controlled by a bigger country with different ideas and ways of doing things.
So, the Soviet Union and Lithuania decided to talk things out and make a peace treaty. This was like a big agreement where they promised to be good to each other and stop fighting. The treaty said that the Soviet Union would recognize Lithuania as a separate country and give it some more independence. In exchange, Lithuania promised to be friends with the Soviet Union and not to cause any trouble.
Overall, the peace treaty was a way for the Soviet Union and Lithuania to make up and be friends again. It was kind of like saying sorry and promising to be better in the future - sort of like when you say sorry to your friend and promise to play nicely together next time.