The Antonine Wall was a big wall built by the Romans a very long time ago to help protect their land in what is now Scotland. Imagine building a big fence around your backyard to keep things out, that's what the Antonine Wall was like.
Now, the Romans back then wanted to protect their land from the people who lived outside of their empire, like the Picts who were a group of people who lived in what we now call Scotland. The Antonine Wall was a wall that went from one end of Scotland to the other, and it was very tall and made of stones and dirt.
The Romans built it to make it difficult for the Picts to get into their land, and it also made it easier for the Romans to control the people who lived on their side of the wall. Think of it like having a playground at school and the wall is the border between your playground and the other one. The wall helped keep everyone playing on their own side.
The Antonine Wall was built a really, really long time ago, around 160 AD, and even though parts of it have fallen down over the years, you can still see some of it today. It's a big part of history and helps us learn about what life was like for people a long, long time ago.