Absolute magnitude is a measure of the intrinsic brightness of a celestial object, such as a star or galaxy. It is defined as the apparent magnitude of the object as it would appear if it were located at a standard distance of 10 parsecs (about 32.6 light years) from Earth. This allows astronomers to compare the true brightness of different objects, regardless of their distance from Earth. Absolute magnitude is an important parameter used in astrophysics to study the properties and evolution of celestial objects.