*A Q-switched laser is a laser to which the technique of active or passive Q switching is applied, so that it emits energetic light pulses. Typical applications of such lasers are material processing (e.g. cutting, drilling, laser marking), pumping nonlinear frequency conversion devices, range finding, and remote sensing.
Note that the article on Q switching contains more details on Q-switching techniques; it also contains a video explaining the basic principle of this method of pulse generation.
Q-switched lasers can be pumped either continuously or with pulses, e.g. from flash lamps (particularly for low pulse repetition rates). For continuous pumping, the gain medium should have a long upper-state lifetime to reach a high enough stored energy rather than losing the energy as fluorescence. In any case, the saturation energy should not be too low, because this could lead to excessive gain, so that the premature onset of lasing is more difficult to suppress. The latter problem can occur particularly for fiber lasers. On the other hand, a too high saturation fluence can make efficient energy extraction difficult.