Pressure Cooking

Boiling point of liquids is reached when the temperature of the liquid reaches a point such that the vapor pressure exceeds the external pressure allowing it to phase shift into a gas. If you increase the external pressure, like inside of a pressure cooker, you need a higher temperature to reach the equilibrium. Thus, the water can be raised passed its normal boiling point allowing the food to be cooked at a higher temperature, speeding up the cooking process.

$\text{Pressure (P)} \propto \text{Heat (J)}$

Therefore, as pressure increases heat increases (and vice-versa). So in a pressure cooker, the heat is increased, and so the water boils fast than in a open surface bowl.

Remember the ideal gas equation pV=nRT means pressure is directly proportional to temperature. Therfore increase in pressure inside cooker increases the b.p. of water.