It corresponds to the highest energy that can be transferred to a weakly bound electron of a detector's atom by an incident photon in a single scattering process, and manifests itself as a ridge in the measured gamma-ray energy spectrum.
It is a measurement phenomenon (meaning that the incident radiation does not possess this feature), which is particularly evident in gamma-ray energy spectra of monoenergetic photons.
The highest energy that can be deposited, corresponding to full backscatter, is called the Compton edge.
[2] In a Compton scattering process, an incident photon collides with a weakly bound electron, leading to its release from the atomic shell.
[2] The part of the spectrum between the Compton edge and the photopeak is due to multiple subsequent Compton-scattering processes.