Simplify the following text for a Grade 12 native English-speaking person.
Original: In thermodynamics , the triple point of a substance is the temperature and pressure at which three phases ( for example , gas , liquid , and solid ) of that substance coexist in thermodynamic equilibrium .
Simplified: The triple point of water or any substance is the combination of temperature and pressure at which it exists in its solid , liquid , and gaseous state all at once , in equilibrium .