Okay, so imagine you're playing a game with your friends. You want to make sure everyone is playing fair and having a good time. That's kind of what the person called the Secretary of State for Commonwealth Relations does, but on a much bigger scale.
The Secretary of State for Commonwealth Relations is like a helper for the government in a country called the United Kingdom. This person helps make sure that other countries in a group called the Commonwealth are getting along with each other and working together nicely.
The Commonwealth is like a big group of countries that used to be ruled by the United Kingdom a long time ago. Even though they're not ruled by the United Kingdom anymore, they still have some things in common and work together on things like trade and helping each other out during tough times.
The Secretary of State for Commonwealth Relations is kind of like a mediator. They talk to different countries in the Commonwealth and help solve any problems they might have. They also work to make sure everyone is following the same rules and working together towards common goals.
So, TLDR: The Secretary of State for Commonwealth Relations is an important person in the UK Government who helps make sure countries in the Commonwealth are getting along and working together nicely, kind of like a mediator in a game you might play with your friends.