Imagine you have a big family and you all live in a big house. But when it's time to make important decisions, like what to eat for dinner or where to go on vacation, it can get pretty hard to make a decision because everyone argues about what to do.
Now imagine that the big house is actually a big area with lots of towns and people living there. But instead of a family deciding things, there are people called "leaders" who make important decisions for everyone in the area. These leaders need to have a place where they can all meet up and talk about the important decisions that need to be made.
That special place where these leaders meet is called the "county seat". It's usually in one of the bigger towns in the area and it's where the courthouse and government offices are located. This is like the living room in your big family house where everyone can sit together and talk.
So when people talk about the county seat, they are talking about the place where important decisions are made for everyone who lives in that area. It's like the grown-up version of your family living room.