The phase diagram below is for the substance water(H2o). The bigger regions in the plot are ice particles, water(H2o), and water vapor. The lines that are separating the bigger regions consist of the melting points, sublimation points, and last of all, boiling points at different temperatures, and pressures.
Matter exists in various forms of phases. If the temperature and/or pressure of a sample of matter is adjusted, the matter may go through a phase transition. During a phase transition, matter shifts between its three states: solid, liquid, and gas.
Note that:
Phase Change Between Two Matters