Brewing apple cider and apple juice is a very old tradition and there are traces from it as early as the 700's. The distillation process is however not a very old knowledge and it was only in the 1500s as a French Count, Seigneur deGouberville distilled apple cider, and thus came up with the first Calvados.
Calvados is not just an apple brandy it’s also a province of Normandy in northwestern France, and that is where the spirits come from. Calvados is usually done in many different varieties of apple, it is not unusual to sometimes use hundreds of different blends. The manufacturer carefully select a good mix between sweet, sour and bitter apples. The selected apples is pressed into juice which is then fermented and becomes cider. The cider is double distilled and stored for at least two years in oak barrels. The best Calvados is considered to come from the area of the Pays d'Auge.
The flavor is reminiscent of cognac with influences of apple and its uses are many. There are many drinks that contain Calvados. Some drink it in coffee, or simply drink it pure. An application that you do not think so carefully about is the cooking. One can usefully flambé with Calvados, use it in sauces or desserts. In principle, one can replace the brandy with Calvados in most recipes to get variety and a new version of a dish.
Something to think about is that the tastiest Calvados emit a smell of apple when you smell it. Another thing that the experts say is that it gets better the longer it is stored. It is not as fussy with how it tastes when used in cooking or in drinks.