The triple point of water (or any substance) is the perfect alignment of temperature and pressure, where water vapor, liquid water, and ice coexist in equilibrium. This occurs at a pressure of 611.657 Pa and a temperature of 32.018 °F (0.01 °C)
If looked at on a phase diagram, like the one below, you can see the triple point of water where all three phases connect. A phase diagram is graphical representation of different temperatures, pressures and the physical states of a substance.
