What is the function of the OFFLINE button in the Vibes Music App?

When you Copy to My Library, you will see the Offline button.  It is always a good idea to turn the Offline button on.  If you were to experience spotty wifi, then your music will still stream even if you lose wifi.  Notice in the picture attached, there are green circles next to each song.  This indicates that the song has been downloaded.   If the circle is not filled in, then the song is not downloaded.    Just keep in mind that licensing restrictions with the original artist music require that those songs/playlists be re-downloaded using the Offline button every 72 hours.