Enabling an infinite loop on Spotify repeats the selected song again and again. If you set an infinite loop for a playlist, all the songs in the entire playlist will be repeated until you stop it. To enable an infinite loop for a particular song, click on the loop icon until you see 1 on the icon. A dot on the loop icon repeats the entire playlist. The infinite loop option is also available in the free version of Spotify. I tried it in the free version.