Okay, so imagine you have a really big house with a lot of land around it. This big house and the land around it is called a "castle" and it's like a fancy mansion that someone really important or rich lives in.
Now, let's say that the person who owns this castle has a lot of power and control over the area around it. They might have other smaller houses and farms, and they make the rules about what people can and can't do in that area.
This person who owns the castle and all the land around it is called the "lord" or "lady" of the castle. They are like the boss of that whole area.
Now, sometimes the lord or lady might be so important or powerful that they are given even more land and control. This bigger area is called a "barony". It's like a big kingdom that the lord or lady is in charge of.
So, putting it all together, the Barony of Corsehill is a big area of land that someone really important owns and controls. And within that big area, there is a really fancy house or castle called the Castle of Corsehill where the lord or lady lives. The lord or lady has a lot of power and control over the people who live on their land and they make the rules about what they can and can't do.