What are “The Legs” of wine?

“Anatomically” speaking, the legs of wine are the tear-shaped drops and streaks that appear vertically on the sides of a glass when swirled. Leg formation is the result of fluid surface tension between alcohol and water. 

Legs typically do not add to or enhance wine quality other than generally indicating higher alcohol content or perhaps a richer texture and fuller body. That’s why they’re especially prominent in fortified wines and high-proof spirits. The quantity and demarcation of legs will vary with the temperature of the wine.