So do you know what a country is? Great, Wales is one of the countries that make up the United Kingdom. Now, imagine a big family, but instead of a mommy or a daddy telling everyone what to do, they have something called a government. The government makes decisions and rules for the family (a country).
In the past, the government that controlled Wales was the same as the one controlling the rest of the United Kingdom. But some people in Wales thought that they should have more say in the decisions that were made about their country. They thought that the people living in Wales would do a better job at making decisions for themselves.
So in 1997, a vote was taken and people in Wales decided that they wanted something called devolution. This means that some of the decisions about how Wales is run will be made in Wales, not in the bigger UK government. Wales now has its own elected Assembly, which makes some important decisions about things like healthcare, education, and housing.
This is kinda like when your mom lets you have a say in what you wear or what you want for dinner. The big family is still in charge, but you get to have some control too. So now Wales is a bit like a big family too, where they have their own Assembly to make some of the decisions, but they are still a part of the UK family.