Protractors are measuring tools used to measure and mark angles, typically in degrees. They consist of a flat, semicircular or circular base with a graduated scale from 0° to 180° or 360°, and a movable arm or straight edge that aligns with the desired angle. Protractors are commonly used in drafting, engineering, woodworking, and metalworking to ensure accurate angle measurements and cuts. Digital protractors are also available, offering precise electronic readings.