What does the term 'legs' mean when describing wine in a glass?

The phenomenon known as legs, the film of liquid on the inside of a glass of wine or spirits that seems to move slowly up and down, is created by the volatile interaction between alcohol and water. Alcohol lowers the attraction between water molecules in spirits and wine, but in the filmy residue on a glass the alcohol evaporates rapidly, leaving behind water molecules that bond more tightly together and tighter to the surface of the glass. The resulting liquid thickens into legs. The more alcohol present, the faster it will evaporate, and the more pronounced the legs will be. Contrary to popular opinion the appearance of legs has no bearing on the quality of wine.