Critical temperature of a substance is the temperature at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied. Every substance has a critical temperature. So it is also a type of temperature which brings about this specific characteristic of substances. For example, critical temperature of oxygen is -119ºC. of carbon dioxide is 31.2ºC, etc.

At normal temperature, say at room temperature, all substances exist in their natural states. For example, oxygen and carbon dioxide are gases at room temperature, iron copper, etc are solids at room temperature, water exists as liquid at room temperature.