Okay kiddo. So imagine there is a big playground with a lot of kids playing together. But there is one kid, let's call him Kid A, who is not happy with how the games are being played. Kid A thinks that he should be the one making all the rules and deciding which games everyone should play.
Now, Kid A cannot just go and grab the toys and make everyone do what he wants. That would not be nice, and nobody would want to play with him. So, what Kid A does is he talks to some other kids that were also not happy with how things are going. He tells them that he has a better way of playing and if they listen to him, they will have a better time on the playground.
These kids start to believe Kid A and they start to follow him. Together, they become a bigger group and start to challenge the rules other kids were following.
This is kind of like Russia and regime change. Russia is a big country that sometimes wants to be in charge of what other countries do. Sometimes Russia does not like the way a certain country is being run and they want to change the leaders of that country.
But they cannot just go and take over the country, that would make other countries angry and nobody would want to work with Russia. So what Russia does is it talks to a group of people in that country who are also not happy with how things are going. Russia promises those people that if they help to change the leader of the country, then everything will be better for everyone.
These people start to follow Russia and they want to change the leader too. Together, they become a bigger group and start to challenge the way things were going in their own country.
So, in short, Russia sometimes wants to be in charge of other countries and they try to influence the people who are not happy with the leadership of those countries to change the leader. It is kind of like a big kid trying to convince some other kids to follow him and change the rules of the games they play.