A cooking apple is an apple that is used primarily for cooking rather than eating fresh. Cooking apples are larger, and can be tarter than eating varieties. Some varieties have a firm flesh that doesn't break down much when cooked. The British grow a large range of apples specifically for cooking, but such varieties are used worldwide, although table (dessert) apples are also used for cooking purposes. Many apples are dual-purpose.
Apples can be cooked down into sauce, apple butter or fruit preserves, baked in an oven and served with custard, and made into pies or apple crumble. In the UK apples are commonly boiled and mashed and served as apple sauce with roast pork. Bramley apple is by far the most popular cooking apple in the UK.
A baked apple is one that has been baked in an oven until it has become soft. The core is usually removed and often stuffed with other fruits, brown sugar, raisins, or cinnamon.