The Kardashev Scale measures a civilization's technological advancement based upon its energy consuption. It was created by Nikolai Semenovich Kardashev, a Russian astrophysicist, in 1964.
A Type I civilization's energy usage meets or exceeds the available energy of an entire planet.
A Type II civilization uses the entirety its host star's energy. Some proposed megascale structures are designed to enclose a star, implicitly making a civilization that constructs them at least a type II.
A Type III civilization uses its host galaxy's entire energy output.
Type 0 is often used to refer to civilizations with energy usage below Type I levels.
Carl Sagan proposed a finer distincton to the scale by calculating consumption versus availability rates to create decimal types. The resulting Kardaschev-Sagan scale requires explicit values for planetary, stellar, and galactic energy as well as total consumption rates. With no other known civilizations, and these values rarely being specified even in hard science fiction, decimal types are almost exclusively used in reference to Earth.
Terrestrial civilization currently rates below Type I on the original scale, and around a 0.72 on the Kardaschev-Sagan scale.