Tequila is a spirit made from the agave plant. The only tequilas worth buying for any drinks listed on this blog are made from 100% blue agave. Ensure that this is stated on the bottle you purchase.
Tequilas have different age statements. Blanco, plata, white, or silver tequila is unaged. These tequilas tend to have the most agave flavor. Reposado tequilas have been aged from between two to twelve months. Añejo and extra añejo are aged more like whiskey for long periods of time in oak.
Joven or young tequilas are blends of unaged and aged tequilas. Oro or gold tequilas are generally mixtos, where only 51% of the volume is blue agave spirit. Mixto tequilas should be avoided.
Añejo tequilas are rarely used in cocktails, and more oftened sipped alone. They may sometimes work well as substitutions for whisky in whisky-forward cocktails.
Technically, all tequilas are mezcals but not all mezcals are tequilas. In practice, mezcals are distinctly non-tequila agave-derived spirits. The main distinction between the two is that tequila is made from blue agave, exclusively. As for flavor, mezcals tend to be thought of as smokier, like a peated Islay Scotch.