Russian interference in British politics means that people from Russia try to influence what happens in British politics. Specifically, this means that they try to make things happen or not happen, such as certain politicians or policies being supported or discredited.
Now, just like how it's not nice for someone to try to cheat in a game, trying to interfere in another country's politics is not a good thing. It can lead to people feeling like their votes or opinions don't matter, and it can make it harder for people to trust what they hear about their government.
So why would Russia do this? Well, some people in the Russian government may want to influence what happens in other countries so that those countries make decisions that benefit Russia. They may do things like spreading false information or supporting certain politicians who are more likely to help Russia.
However, it's important to remember that not everyone from Russia is involved in this kind of interference, and it's not just Russia that tries to influence other countries' politics. It's important to stay informed and think critically about what we hear and read about politics, whether it's from Russia or anywhere else.