Question

What is meant by the term apparent brightness (apparent magnitude)?

Answer 1

The apparent brightness is how much energy is coming from the star per square meter per second, as measured on Earth. The units are watts per square meter (W/m2). Astronomers usually use another measure, magnitude

Answer 2

The apparent magnitude (m) of an astronomical object is a number that is a measure of its brightness as seen by an observer on Earth. The brighter an object appears, the lower its magnitude value (i.e. inverse relation). ... The measurement of apparent magnitudes or brightnesses of celestial objects is known as photometry.