Okay kiddo, do you know what a settee is? It's like a big comfortable armchair. But a settee sail is a bit different.
Imagine you're on a big boat in the water. It's really windy, and you need to move the boat forward. One way to do that is by setting up a sail. A sail catches the wind and pulls the boat forward.
Now, a settee sail is a type of sail that's used on boats with more than one mast, or "poles" that hold up the sail. The settee sail goes between the front mast, called the foremast, and the second mast, called the mainmast.
The settee sail is shaped kind of like a big triangle, with the pointy end at the top and the long end at the bottom. It's made out of a special fabric called canvas that's really strong and can stand up to the wind.
When the wind blows into the settee sail, it fills up like a giant balloon and pushes the boat forward. The sailors can adjust the settee sail by pulling on ropes called sheets that are attached to the corners of the sail. That way, they can catch even more wind and move faster through the water.
So that's a settee sail, an important part of sailing that helps move boats forward using the power of the wind.