An angle grinder is a tool that helps people shape, sand, and cut things like metal and wood. It is kind of like a special electric kitchen mixer that has a spinning blade on the bottom that can be attached to different kinds of wheels depending on what you want to do with it.
When you need to use it, you press a button to turn the grinder on and then you can control how fast the blade spins by pressing on a little lever. The blade is really sharp and can be dangerous if you're not careful, so it's important to wear special protective gear like gloves and goggles when using it. You also need to make sure the workspace is clear and nobody is around before you start using it.
Angle grinders are cool tools that adults can use to make really cool things, but they are not toys, and children should never use them without adult supervision.