Imagine you and your friends want to pick a playground to go to. You realize that some of your friends want to go to one playground, while others want to go to a different one. So, you decide to have two groups - one that goes to Playground A and another that goes to Playground B.
In Wales, the grown-ups need to do something similar when they go to vote. They need to pick who they want to represent them in the Senedd, which is a big group that makes decisions for Wales. But because there are many different kinds of people in Wales, they need to make sure that everyone's voice is heard.
So, they decided to divide the country up into different areas called constituencies. Each constituency is like a different playground that people can vote for who they want to represent them in the Senedd. For example, kids who live close to Playground A can only vote for who they want to represent them in Playground A, while kids who live close to Playground B can only vote for who they want to represent them in Playground B.
But, they also wanted to make sure that smaller groups in Wales, like people who speak Welsh, have a say in who represents them. So, they also divide Wales into different regions, like North Wales or South Wales Central. Each region has more than one playground, but people in those regions can vote for who they want to represent them in the Senedd for all the playgrounds in that region.
So, basically, senedd constituencies are like playgrounds that people can vote for who they want to represent them in the Senedd, while electoral regions are like groups of playgrounds where people can vote for who they want to represent them in the Senedd for all the playgrounds in that region.