A sabre saw is a tool that helps you cut things. It is like a smaller and more portable version of a big saw. Instead of having a long blade that you move back and forth by hand, a sabre saw has a shorter blade that moves very fast and up and down on its own.
Imagine you have a piece of wood that you want to cut into a certain shape. You would use a sabre saw to make that cut. First, you attach the blade to the end of the saw. Then you turn the saw on, which makes the blade start moving up and down very quickly. You hold the saw with one hand and guide the blade with the other hand, slowly cutting through the wood.
You can use a sabre saw to cut a variety of materials, including wood, metal, plastic, and even some types of tile. They are really helpful for making detailed cuts or cutting curves or angles in the material you are working with.
But remember, a saw is a tool that can be dangerous if not used properly. Always make sure you have a grown-up or someone who knows what they are doing to show you how to use the saw safely.