What is the difference between Tequila* and mezcal? Dozens of distilled agave plants make up a broad category of spirits called mezcal, an incredibly specific subsection of mezcal is tequila. A perfect analog is found in whisk(e)y. Whisk(e)y is a family that includes, single malt, Bourbon, Canadian, Scotch, blended whisk(e)y, Irish Whiskey and I'm getting bored of listing whisk(e)y styles.
I'm in Colorado right now. My dog has been playing with my neighbor's wolf-dog. It's a fun coincidence because when lil' Pip is doing something extra cute, I will rub her belly and say, "you used to be a wolf." An overly simplistic metaphor to explain Tequila is here: like all dogs descended from wolves, all mezcal (and thusly, Tequila) descend from one type of agave called Agave** angustifolia, or commonly espadin. So, when Pippin and Maya are sunbathing, they are a wolf pack.
Even though Tequila, specifically the plant it is made from (Agave tequilana, commonly: blue agave) evolved from espadin, Tequila is very narrow. Not unlike a dog breed, get it? So Tequila is always made from just one plant- Agave tequilana, produced in only five Mexican states and must fit within one of the five styles recognized by the Mexican government. But what are those states, styles and other whatnots? Tune in later to find out!
*"Tequila" is a class of spirits that has a specific geographic origin. As such, I capitalize it. You will find most writers do this at random; those people are fucking stupid. Hey, I have issues with dyslexia, in addition to which, over policing grammar is classist. So, if you ever see the words Bourbon, Cognac or even Scotch, written in lower case, that is incorrect.
**The genus is capitalized in Latin names.