The brightness of a star is commonly expressed using a measurement called "magnitude." There are two primary types: apparent magnitude, which describes how bright a star appears from Earth, and absolute magnitude, which measures the star's intrinsic brightness at a standard distance of 10 parsecs (about 32.6 light-years). The magnitude scale is logarithmic; a difference of 5 magnitudes corresponds to a brightness factor of 100. The scale is counterintuitive, with lower numbers indicating brighter stars and higher numbers indicating dimmer stars. This system allows astronomers to categorize and compare the brightness of celestial bodies effectively.