Tequila is so much more than the rot-gut they serve at the bar for a quick drunk.
Like champagne, tequila is a 'controlled appelation', meaning that only liquor that is distilled from agave plants near Guadalajara, Mexico can carry the name Tequila. Monte Alban (yes, the one with the embalmed worm
) is also a tequila, but can't legally call itself that, so it goes by the name 'mezcal'.
Patron is one of the high-class, top-shelf super premium tequilas. Cuervo is your garden variety stuff, though they have various degrees of quality.
Here's a site with all the info you need to know to be an educated tequila swiller...
http://www.tastings.com/spirits/tequila.html