What is absolute or kelvin scale of temperature?

With a temperature of absolute zero  (i.e. –273°C) as the lowest temperature, a new scale for expressing the temperature has been developed which is called absolute scale or kelvin scale and the temperature expressed on this scale is called absolute or kelvin temperature.
In the kelvin scale, the size of the degree is kept the same as on the celsius scale but the zero is shifted to –273·15 below zero on the Celsius scale.
Thus,  –273.15° C = 0 K
or         0° C   = 273.15 K
or         t° C = (273.15 + t) K

Hence temperature on absolute or kelvin scale may be obtained by adding 273.15 to the temperature on celsius scale. 
T_K = 273.15 +  t°C
In practice, the above relation is generally taken as
T_K = 273 + t° C where T is the temperature on kelvin scale and t is the temperature on celsius scale.