When we perform cooking on devices such as in the oven, the temperature is considered as the cooking temperature or the normal temperature?  For example, when I cook a potato in the oven in a temperature at 15 degree Celsius, is it the same than putting a potato in a room at a temperature of 15 degree Celsius? 
Cooking normally involves higher heat than you would feel comfortable in a room; the application of heat is what changes the molecular structure of food and kills bacteria, making it both tasty and safe to consume. There's otherwise no real magic to it: if it's a hot enough day outside, you can put a frying pan on the hot pavement in a parking lot and fry an egg in it as though it were on the stove. If for some reason the apocalypse was happening and it were 350F outside, you could bake a cake the same way. But you'd probably be dead.  