To put it simply, certain minerals (quartz, feldspar, and calcite), store energy from the sun at a known rate.This energy is lodged in the imperfect lattices of the mineral's crystals.
Luminescence dating (including thermoluminescence and optically stimulated luminescence) is a type of dating methodology that measures the amount of light emitted from energy stored in certain rock types and derived soils to obtain an absolute date for a specific event that occurred in the past.
This dating method is also known as Archaeological Dating or Historical Chronology. These methods were relied on especially prior to the introduction of scientific methods of dating.
But, even when the scientific methods of absolute dating are available, this method of dating has not lost its importance, as many a time we have to depend solely on relative dating.
The method is a direct dating technique, meaning that the amount of energy emitted is a direct result of the event being measured.
Better still, unlike radiocarbon dating, the effect luminescence dating measures increases with time.
Even when the absolute dates are available, we have to supplement the information with relative dating.