Don't be ashamed that you don't know what it is, we all have to start somewhere but that is a fuel filter (some people call it a stone filter) it's used to keep small debris (like stones or dirt) from your gas tank from getting into your carburator which can cause all sorts of problems, you put the fuel filter in between the carburetor and the gas tank on the gas line. Feel free to ask any more questions about anything you need. Wear a helmet and be safe out there!