Okay kiddo, so let's talk about Welsh lost lands. You know how sometimes you might lose a toy or a book and it's hard to find it? Well, something like that happened in Wales a long time ago, but with land.
A long, long time ago, there were some lands in Wales that belonged to the Welsh people. But then some people from another place called England came and took some of that land away from the Welsh people. This happened a few times over many years.
So, imagine Wales is a big pie, and England came and took some slices of that pie away. The Welsh people didn't like it, but they were not as strong as the English at the time, so they couldn't do anything about it.
Now, even though the Welsh people lost some of their land, they still kept their language and culture strong. They told stories about their lost lands and kept that part of their history alive.
So, think of it like this: the Welsh people used to have some pieces of land, but then some other people came and took those pieces away. The Welsh people were sad about it, but they still kept their culture and memories alive.