Tequila is a Mexican distillate from the agave plant. By law, in order to be called tequila, at least 51% of the material must be from the agave plant, and the rest (water, sugar, oil, gasoline etc.) can be added at the discretion of the distiller. This is one reason why "100% agave" is a good thing to look for on the label.
How is it made?
The agave plant is harvested, and the spiked leaves (pencas) are cut off with a long handled machete. When finished, the agave plant resembles a huge pineapple, the piña. These are then mashed up and then cooked in brick ovens, hornos. The cooked agave is then mixed with water, and then goes into stills, where it ferments for several days. (At this time, additives are sometimes used as well.) Finally, it goes to bottling, or if to be aged, is put into barrels. Where is it made?
Legally, tequila is only made in the Mexican state of Jalisco. The laws have appeared to have been relaxed somewhat, as you can now find "tequila" from Aguascalientes and other states.
What is this NOM thing on the label?
NOM stands for Norma Oficial Mexicana. This number is assigned by the Mexican goverment to the distillery to identify it's products. All legitimate tequilas produced and bottled in Mexico will have this on the label. This is very useful when trying to dertermine the general quality and taste of an unknown brand, because most house styles are will be consistent across the product line. Most of the "generic" stuff imported into the US lacks this marking, probably because the tequilero in Mexico would be embarassed if the product was traced back to his distillery. Click here to see a list of the most common.
What are the classifications of tequila?
There are basically four styles of tequila:
Blanco or Silver is the familiar crystal clear that comes from the
still, and can be aged in tanks up to 60 days. A well made blanco will
be harsh with a peppery finish, but will display the full flavor and
aroma of the agave. A poorly made blanco (which is usually the
majority) will give you an instant brain seizure.
Joven Abogado or Gold is mostly made for the foreign markets. This
is basically a Blanco with caramel additive for coloring, which also tends
to reduce some of the harshness. However, the additional sugar may lead to
a hangover.
Reposado (rested) is tequila that is aged in tanks or barrels for a
minimum of two months. The finer brands, such as Herradura, will be aged
in wood barrels (usually oak) for around 11 months. The key here is
balance. A well made reposado should retain much of the agave flavor,
but should have a smooth finish. If the house style is 100% agave,
then the reposado process should provide natural coloring due to the
aging in wood barrels. Herradura, since it is usually aged longer,
will often be darker than other reposado brands.
Añejo (aged) usually remains in the barrels from 2-6 years,
with 2-3 being the norm. Despite the aging, depending on the house style,
it may still have a "hot" finish, however in general it will be smoother
than other styles. The super premium añejos are generally very
smooth, and should be sipped like a fine brandy.
What's all this about lime and salt?
Lime and salt are traditional additives, but are in fact optional with the finer brands. The basic logic is to lick the salt first, which gets the saliva going. Then you slam down the shot, and finish by sucking the lime, which should soothe the burning in your throat. Sounds pretty grim, but if you're drinking a cheap or non-aged tequila, it's necessary. As mentioned, the finer tequilas are best taken without lime and salt, so that you can appreciate the subtle flavors and aromas.
Now really, what kind of additives are used?
It really depends on the brand. If your're talking about 100% Blue Agave from Herradura, the answer is simple: none. Most non-premium brands however will add something. Caramel (for coloring) and water (to reduce alcohol content down to 40%) are the most common. Of course, who knows what other crap might be put in, so you take your chances. A few brands, such as Cuervo Mistico also add orange or lime flavoring. While this does not necessarily make it crap, it does change the emphasis.
What happened to the worm in the bottle?
If there's a worm in it, it's NOT tequila, no matter how it's marketed. Basically, you've got mezcal, which is a related distillate, but is barely drinkable.