Both ways of making X-rays involve a change in the state of electrons. However,
Bremsstrahlung is easier to understand using the classical idea that radiation is emitted
when the velocity of the electron shot at the tungsten target changes. The negatively
charged electron slows down after swinging around the nucleus of a positively charged
tungsten atom and this energy loss produces X-radiation. Electrons are scattered
elastically or inelastically by the positively charged nucleus. The inelastically scattered
electron loses energy, and thus produces X-ray photon, while the elastically scattered
electrons generally change their direction significantly but without loosing much of
their energy.