Mezcal is part of the Mexican culture. It may be a popular saying, a social icon, a toast, there's always mezcal, or tequila for that matter.
Just as Cognac is a special type of brandy produced from specific grapes grown in a select region of France not all brandy has the distinction of being Cognac. In like manner, all liquors distilled from any agave plant are "mezcal", but only those made from the blue agave are branded as Tequila, all the others are mezcal. The most famous mezcal is distilled from a variety of agave grown in the state of Oaxaca in southern Mexico, and the finest comes from the wild agave known as "papalomé" that it is so potent that two shots can really knock you down!
The language of tequila can be very confusing. To begin with Tequila is the name of the town where production originally began, and it is also the name of the volcano overlooking this town. Locals in the Tequila Region refer to the blue agave plant as "mezcal", and the fields where this plant is harvested are known as "mezcaleras". Many distillers call to the distilled liquor mezcal and is only called tequila when finally bottled. Before tequila became known as it is today, it was called "vino mezcal" or mezcal wine.