Metering: Peak, RMS and LUFS

The peak of an audio signal is its loudest point. The peak value is a momentary measure of the loudest point. Root mean square (RMS) and loudness units full scale (LUFS) are measurements of an average signal level based on what our hearing is accustomed to. RMS is an accurate representation of the average loudness of your mixes though LUFS is considered a more accurate way of measuring perceived loudness. LUFS is the standard by which online streaming services such as YouTube and Spotify measure the perceived loudness of tracks. This is not to force you to listen at any particular volume, but moreover to ensure a relatively consistent level across different tracks.