Mezcal is a spirit distilled in mexico from agave plants. Its sister product, Tequila, is also a product of agave but it is limited to a geographical area called tequila and must be made from a particular type of agave called the "Blue Weber Agave." Mezcal can be made in a larger geographical area of Mexico and may be made of several different types of agave plant. The term "Mezcal" is an indigenous word for the agave plant. The agave plant is also known as the "Maguey" as well. The primary area for production of Mezcal is Oaxaca. To produce it, the mature agave plants are stripped of their leaves, and then the the hearts are baked to convert starches in the plant into fermentable sugars. They are then left to ferment, often naturally from airborne yeasts, and then crushed to release the then fermentable juice. Traditionally the hearts were cooked in pits fired by wood, but many modern producers use steam and steel ovens.
Many mezcals are bottled with a worm inside. The tradition's history is often speculated upon and the best reason I have heard is that the worm used to be added because when added to a mezcal that had fermented cleanly it would not decay. Perhaps before we had chemistry labs you could tell if your mezcal was good if its worm was intact. The worm is often added to modern bottlings. Some think of it as a gimmick for marketing but it has no bearing on product quality in and of itself.
Often very earthy and smoky. Agave plants can have smells ranging from classic "wet cement," which is agricultural in nature but very complex and interesting, to tropical fruit and citrus fruit aromas, and sometimes spicy or sweet notes as well.
Many mezcals are released un-aged and clear but some are aged in wood and obtain light brown or golden coloring from the barrrels.
There are many types of agave used, and the flavors range greatly as a result. Some are very smoky and some are clean and crisp, with tropical fruit notes and spicy alcohol.
Varys greatly. In the U.S. many examples are 40% alcohol by volume.