Characteristic X-rays formed from interaction in electron orbitals

Characteristic X-rays are distinctive

Continuous X-rays formed from nuclear interactions of electrons

Electrons may interact with the electron orbitals of the atom to eject an electron (thereby causing an ionization event). When that electron is replaced by another from an outer orbital, the energy lost by the outer orbital electron is converted into an X-ray photon. Such X-rays are labeled as K-alpha, K-beta, L-alpha, L-beta, etc., and have characteristic energies for each element. Thus, these X-rays carry specific information about elemental composition.

Continuous X-rays are formed when a high energy electron loses energy during its interaction with an atomic nucleus. A range of different energies are generated which carry information about the mass of material irradiated, but nothing about the elemental composition.