While tequila is required to be made from blue agave, most (but not all) mezcal is made from a variety called espadin, and it must be made in a certain region in Mexico, the most well-known of which is Oaxaca.
Espadin takes eight years to grow to maturity, though other varietals can take longer. Once it’s mature, the spines are cut away, exposing the hearts -- piñas -- which are buried in smoky fire pits and covered. The agave cooks from anywhere between three days and two weeks, as the starchy plants are converted into soft, sweet, pulpy fruit. (Tequila, on the other hand, is cooked for far less time in a more conventional oven.)
Then it's crushed by a large stone wheel pulled by a horse or donkey (or Conan), producing fermentable juice, which is paired with wild yeast, then distilled in clay or copper stills. Once it has been twice distilled, it's bottled, though some get barrel aged.
Not all mezcal is made this way, but the best is. This is the stuff that comes from smaller heritage farms, where each mezcal has been made its own way for generations. It's drunk to celebrate births and deaths, harvests and weddings.