Okay kiddo, so imagine you're walking outside and you see a really long wooden path on the ground. This is called a plank road.
Now, sometimes when people are traveling from one place to another, they need to cross places where the ground is really soft or muddy and it's hard to walk or drive through. A plank road helps solve this problem because it's made up of flat pieces of wood placed close together on the ground. This makes it easier to walk or drive over the soft or muddy ground.
Plank roads were used a lot in the olden days when cars and trains didn't exist yet. People and horses had to travel long distances on foot or by carriage and sometimes had to cross swamps or muddy areas.
Today, we don't really use plank roads anymore because we have better tools to make roads that are stronger and last longer. But they were pretty cool back in the day!