Brightness of stars

What is the difference between apparent and absolute brightness of a star? What is the mathematical relationship that links the two?  The brightness of an object as it naturally appears in the sky is the apparent brightness or it is how much energy comes from the star per square meter per second, as measured on Earth. The units are watts per square meter The apparent brightness a star would have if it were placed at a standard distance of 10 parsecs from Earth is called absolute brightness. Apparent brightness is directly proportional to the luminosity divided by the square of its distance. Mathematically: ApparentBrightness (Energy Flux)  ∝Luminosity / Distance 2