A pressure cooker works by trapping steam, which increases the internal pressure. This higher pressure allows the boiling point of water to rise above 100°C, thus cooking food faster. The weight of the lid is crucial as it determines the pressure threshold at which the safety valve releases steam. The area of the hole in the lid also influences the rate at which steam escapes and thus the pressure buildup. The external flame temperature, while important for heating, does not directly dictate the cooking temperature inside the cooker once the pressure is stabilized; the cooking temperature is governed by the steam pressure.