Just going to rip through the latest announcement from Spotify and provide some commentary as I do so. Take from it what you will. The original announcement is here: https://www.spotifyforbrands.com/en-US/news/sai-announcement
LUFS is a measure of average loudness over time. If your audio has a LUFS of -14 it means that, on average, over the full duration of an audio file, the listener was experiencing -16LUFS (perceivable).