At what standard, fixed distance is a star's Absolute Magnitude ($M$) defined as its apparent magnitude?

Answer

10 parsecs

Absolute magnitude standardizes brightness measurement by calculating what the apparent magnitude would be if the star were placed at a fixed distance of exactly 10 parsecs from Earth.

At what standard, fixed distance is a star's Absolute Magnitude ($M$) defined as its apparent magnitude?
astronomystarbrightnessScalestellar magnitude