W indicates Men’s or Women’s Sizes. Other systems are for either gender. A shoe size is an alphanumerical indication of the fitting size of a shoe child shoe size chart us a person.
Often it just consists of a number indicating the length because many shoemakers only provide a standard width for economic reasons. There are several different shoe-size systems that are used worldwide. Only a few systems also take the width of the feet into account. The size of the left and right foot is often slightly different. In this case, both feet are measured, and the shoe size is based upon the larger foot.