A very simple thermodynamic model of a planet, which includes first order approximations of its radiation balance (black bodies), including two radiation modulating effects i.e. albedo and green house and two heat storages (ocean and atmosphere). It is a lumped model which does not consider spatial variations and resulting mass transports - thus no heat exchange between e.g. equatorial and polar regions...
As a consequence all values are surface specific i.e. per square meter. E.g. the energy balance is the balance in W/m² and the heat reservoirs are water and air columns with a cross section of 1 m²...