What does the scale named after Soviet astronomer Nikolai Kardashev (1932–2019) in 1964 measure?

The Kardashev scale is a method of measuring a civilization's level of technological advancement based on the amount of energy it is capable of using. The measure was proposed by Soviet astronomer Nikolai Kardashev (1932–2019) in 1964 and was named after him.

The scale is hypothetical, and refers to energy consumption on a cosmic scale. Various extensions of the scale have since been proposed, including a wider range of power levels (Types 0, IV to V) and the use of metrics other than pure power (e.g., computational growth or food consumption).