A yo-yo is a popular toy consisting of two discs connected by an axle, with a string wound around it. When the yo-yo is thrown down, it unwinds and spins, then can be pulled back up by the string. This simple mechanism allows for various tricks and stunts, making it a favorite among children and adults alike. Yo-yos come in different shapes, sizes, and materials, including plastic and wood. They can be classified into two main types: responsive and unresponsive. Responsive yo-yos return to the hand with a gentle tug, while unresponsive yo-yos require more advanced techniques to bring them back.