The main control screen allows you to control playback and volume, set song ratings, and toggle the settings of the active playlist. Using the playback controls you can play or pause the currently playing song as well as advancing forwards or backwards within the playlist.
Tap once on the album art to display the additional controls. From here you can adjust the volume, rate the current song, and toggle the playlist's shuffle and repeat options. Tap on the album art again to hide these controls.
You can also tap on the song name in the header bar to open the playlist view, automatically scrolled to the location of the currently playing song.