Mastering engineers make subtle EQ and compression adjustments, set final loudness with limiting, and check that a track translates across speakers, headphones and phones.
Most streaming platforms normalise playback loudness, so extreme loudness no longer gives an advantage. A balanced master with healthy dynamics usually sounds better after normalisation.
Using it in a prompt
Ask for a "dynamic master" for film and documentaries or "punchy, loud master" for club and gym use.