Have you ever seen an old train that looks like it could break down at any moment? Well, sometimes people take those old trains and fix them up so they look and work like new again. That's a restored train!
Picture a really rusty and dirty train. It looks like no one has used it for many years. Maybe the seats are torn and there's dust all over the place. But then some really clever and handy people come along and clean it up, fix all the broken parts, and repaint it so it looks shiny and new. They might even replace the old coal engine with a more modern one.
After all that work, the train is restored and ready to go back on the tracks! People can ride it just like they used to a long time ago. Restoring a train can take a lot of time and money, but it's worth it to bring a piece of history back to life.