The true brightness of a star, as opposed to the brightness seen from Earth (apparent magnitude) i.e. the brightness of a star when observed from a standard distance of 10 parsecs or 33 light-years. From that distance the apparent and absolute magnitudes of a star are the same. The brighter the star, the smaller the number of magnitude.
Though the apparent magnitude of the Sun is -26.78 its absolute magnitude is only 4.74. Compare to the brightest star on the night sky, Sirius, -1.46 and 1.4. This means that Sirius would be about 100 times brighter from the equal distance.
