"Aged" or Anejo, Tequila rests in oak barrels for at least a year. This causes the agave to lose its properties, add the barrel's flavor, and take the amber color. The result is a smooth and rich tequila with caramel and butterscotch hints. Don't you dare mix this tequila with anything.
Añejo is basically when Tequila reaches adulthood. It's like when you grow up and lose innocence and are full of luggage, but in this case, the luggage is delicious and does not require therapy.