There are so many different varieties, but apples are usually categorized as 'table', 'cooking', or 'cider' apples.
'Table' apples are enjoyed raw and are quite sweet compared to other types. This group includes Red Delicious, Fuji, Cortland and Gala.
'Cooking' apples are used for just that (cooking), they're slightly bigger and more bitter than those eaten raw. Some of the common ones found in the store are Bramley, Granny Smith, Gravenstein, and Jonathan.
'Cider' apples have been developed specifically for making apple cider. This fruit is usually dry and bitter, which doesn't make them a popular choice to eat raw. But because of their high acid levels and sugar content, they are good for alcohol production! A few examples of cider apples are Sweet Alford (sweet), Backwell Red (sharp), Brown Snout (bittersweet) and Foxwhelp (bittersharp).
Because apples are so versatile, it can be difficult to decide whether you need a 'table' or 'cooking' apple if the recipe doesn't specify. The general rule of thumb is to use 'cooking' apples if you prefer a moist, softer textured dish and 'table' apples if you want your apples to retain their shape.