A yo-yo is a toy that is made up of two identical discs connected with an axle, around which a string is wound. The basic design has been used to make toys for many centuries, and on several continents, as paintings and drawings from China, Europe, and Africa suggest. The modern design is somewhat more streamlined, and some specially designed yo-yos have unique features, but it is essentially a toy that could be made at home, with some effort. People of all ages around the world use these toys, although most players start when they are young.
The core of a yo-yo is the axle, which is attached to two discs, made from metal, wood, plastic, glass, or ceramic materials. The discs are equally weighted so that they will balance, and they are frequently decorated with painting or carving. Some modern toys light up during use with the addition of small LEDs on the inside. A length of string is attached with a slip knot on one end for the player to grasp, and a loop to go around the axle.
The loop of string around the axle contributes to the flexibility of the toy. The use of a loop, rather than a knotted tie, was pioneered in the Philippines, and it is known as a looped slip string. Because the string is looped, the axle can rotate freely inside of it, allowing the yo-yo to spin when it reaches the end of the string, rather than just stopping. This is known as sleeping, and is the foundation of many tricks, including the most basic trick, in which the yo-yo is brought back up the rope and into the player's hand.
To use a yo-yo, the string is wound around the axle and the loop on the free end is placed over the finger of the player. The hand is held palm down, with the toy lightly grasped, and then it is gently tossed towards the ground. The string unwinds as the device travels, until all the string has been played out and the yo-yo stops. Many players learn to do fancy tricks, some of which are quite complicated, and strut their stuff at competitions around the world.
