Temperature typically refers to the average quantity of kinetic energy in the vibrating particles-such as electrons or entire atoms-of a mass.
There are various references for temperature measurements, such as the freezing point of water. In thermodynamics, the theoretical threshold of “Absolute Zero” is commonly used due to its foundation in physics and the International System of Units (known as “SI”).
The lowest theoretical temperature of matter is a threshold at which a mass has no surplus kinetic energy to transfer. That state is known as “Zero Kelvin.”
Temperature Kelvin is widely referred to as absolute temperature, and is not expressed in degrees (°).
This video (4:07) explores temperature scales and Absolute Zero.