An oven is a device for baking food using heat. You probably scramble eggs on your stove but bake cupcakes in your oven.
Most ovens are in kitchens, whether in private homes or restaurants. Every once in a while, you'll see an outdoor bread or pizza oven too — these are built of brick, stone, or clay, and can safely get hot enough to bake at very high temperatures. Another kind of oven is one that's used for baking ceramics, which is also called a kiln or sometimes a furnace. The very oldest ovens were built thousands of years ago in Central and Eastern Europe.