Temperature is the measure of kinetic energy of molecules. According to zeroth law of thermodynamics, if A&B are in thermal equilibrium and B&C are in thermal equilibrium then A&C are in thermal equilibrium .This idea led to the development of thermometer.If B is thermometer then A&C are at the same temperature without actually being in contact. Water being abundant and easily available was used to calibrate the thermometer. Celsius scale and Fahrenheit scale were developed using water as reference substance. In the Celsius scale, the freezing point  of water is marked as 0 deg C and the boiling point of water as 100 deg C. The problem with using water as a reference substance ;1)BP and MP of water are a function of pressure and temperature .2) what if we want to measure the temperature of a distant planet which is devoid of water. This lead to the development of absoulte temperature scale /kelvin scale. Kelvin scale is based on  activity of atoms. At 0K, all substances have minimum molecular activity irrespective of the nature of atoms(element) . 0K is - 273 deg C
Absolute is the lowest temperature at which the system is in a state of lowest possible energy it is represented by vo.The degree or intensity of heat present in a substance or object is called temperature.