In physics, energy scale is a particular value of energy determined with the precision of one order (or a few orders) of magnitude. Different phenomena occur at different energy scales. The typical energies of all phenomena that occur at the same energy scale are comparable.
The observation that different phenomena should be organized according to the energy scale (or, equivalently, the length scale) is one of the basic ideas of the renormalization group.
For example, the QCD (energy) scale is around 150 MeV, and the masses of strongly interacting particles (such as the proton) are roughly comparable. The electroweak energy scale is higher, roughly 250 GeV. The Planck scale is much higher yet - about 1019 GeV.
