Pulque is known as the drink of the gods, a Mexican Ambrosia, so to speak. This drink dates back about a thousand years. The drink was considered sacred and a privilege reserved for the upper class. Unfortunately, the beer industry spread a lot of stories about pulque and how it had cow excrement in it and pulque started being seen as low-class. Pulque is the fermented sap of the agave plant. Think of what beer is to whiskey. Pulque is that to tequila and mescal. Pulque is usually made in a number of delicious flavors called curados. It's low proof, usually 3-5%. It's also pretty healthy, almost like a slightly alcoholic smoothie.
Mezcal or Mescal is actually the original form of tequila. Much like how brandy is the basis for Cognac. All tequila technically is mezcal but produced in the designated regions around tequila Mexico. Tequila is a protected term, enforced by the Mexican government, while mezcal is not. The CRT, Consejo Regulador del Tequila (tequila regulatory council), makes frequent inspections on every aspect of tequila production to allow the producers to sell their product as tequila. Mezcal doesn't have that. Now you might think that this inherently makes tequila a better product but that's not necessarily the case. Tequila has to use at least
Many modern mezcal producers have actually created products that rival and even dwarf the quality of some tequilas. For a while the only brand of mezcal I could find was Monte Alban, which was a decent mezcal, but these days you can find all sorts of premium brands, like Wild Shot, Ilegal, and Joven. While tequila can only be made with the Weber Blue Agave, mezcal can be made from any of dozens agave plants, but most commonly the green agave, or Agave Angustifolia. It is effectively still just distilled Pulque. It's made mainly in Oaxaca and has a stronger smokier flavor than tequila. It also has the worm. Yes, this is where the worm in the bottle comes from. It won't hurt you; drink it once.
Bacanora at its foundation is just a different genre of Tequila. Bacanora was named after a town where it was popularly produced. Today, it is a protected term ensuring that is only made using the certain agave grown in the select northwestern regions of Mexico, the agave Pacifico or Agave Yaquiana. It is another government regulated name that ensures that the product is only made to certain standards. It terms of flavor it's a bit more robust than most tequilas but not quite as harsh and smokey as many mescals.
Sotol is worth mentioning as well. Sotol is another distilled Mexican spirit made and distilled in very much the same vain as mescal and bacanora. It technically doesn't use the agave plant, however. It is made from the Desert Spoon, or Dasylirion Wheeleri, which is a type of evergreen shrub common in North Mexico and parts of Texas. This plant was originally fermented some 800 years ago. It started being distilled in the 16th century when the Europeans brought over distillation techniques. The production of this spirit is nearly identical to mescal down to the way it's harvested and trimmed. Much like tequila, it is put in three different age classifications: Plata, Reposado, and Anejo. Sotol is generally slightly smokier and more vegetal in flavor than the average tequila.