A protractor is a simple tool used in geometry to measure angles. It usually has a semi-circular shape marked with degrees from 0 to 180. To use a protractor, you place the center hole over the angle's vertex and align one side of the angle with the zero line. Then, you can read the measurement where the other side crosses the degree scale. Protractors come in various materials, including plastic and metal, and are often found in classrooms alongside other tools like rulers and compasses. They are essential for students learning about shapes, lines, and angles, helping them understand the basics of geometry and improve their math skills.