Luminescence is the eye-catching phenomenon of light emission by a mineral after some input of energy (the excitation). Although commonly used in Earth sciences only to produce images, much more can be extracted from this phenomenon. Luminescence is extremely sensitive to low levels of emitters (activators), which helps to reveal the geochemistry or the creation of defects. We give an overview of the great variety of techniques (cathodoluminescence, photoluminescence, and more), discuss vocabulary issues (such as excitation versus stimulation, or the different types of persistent luminescence phenomena), and propose wording we feel best reflects today’s knowledge. We explain the basics of luminescence spectroscopy with emission, excitation, and time-resolved spectra to obtain useful data for Earth scientists.