For example, "water" in our daily life can be in a liquid state, but as the temperature of the same water decreases, it can change to a solid state called "ice", and as the temperature is increased, it can also change to a gas state called "water vapor".
The same substance called "water" has completely different physical characteristics depending on the condition of temperature. This transformation of the same substance into a state (form) with different characteristics is called a phase transition.
In phase transition, the change to a liquid is called "condensation" and the change to a gas is called "evaporation".