They are divided generally in two qualities:
1. Tequila:
A blend of minimum 51% pure Tequila from the blue agave.
(Agave Tequilana Weber, blue variety)
2. Tequila 100% Agave:
Is distilled entirely from the blue agave (Agave Tequilana Weber, blue variety) and bottled in the denomination of Origin, this has to be mentioned on the label of the bottle.

These qualities are furthermore distinguished as followed (CRT):
Tequila: silver or blanco
gold, joven or oro
Tequila 100% Agave: silver or blanco
aged oder reposado
extra-aged or aņejo

After a double distillation process the Tequila is transformed to the above mentioned "nuances" of taste.
The first possibility is to bottle the Tequila directly after distillation and blending. This would be a Silver or "Blanco". The "Gold" Tequila is actually a "silver" one, to which is added caramel (burned sugar used for coloring and flavoring food) in order to give the tequila look of aging.
Tequila 100% Agave
If the Tequila 100% agave it's bottled after his double distillation, than do we have a "White" or "Silver" Tequila, or in Spanish "Blanco". "Aged" or "Reposado" thereagainst has to be placed in storage after distillation for at least two months in an oak-barrel.
The third and most extravagant and time consuming method for a Tequila 100% agave it's his maturation in a white oak barrel for a minimum of one year. The oak barrel may not hold more than 600 liter. A tequila who was stored in such an oak barrel, and was inspected periodically during this time by the CRT has the privilege to be called "Extra aged" or "Aņjeo".