In the musical genre tab, you can see everything that's available. Just select one to see all the songs within that genre. You can also add songs to your favorites or save them to return to them more easily later on.
The playlists have to be created beforehand by adding songs. On the favorites tab, you'll see any song you've marked with a heart, while in the history tab, you'll see the last few songs you've listened to. While you listen to a song, you can see it at the bottom of the screen.
In addition to the songs offered by the app itself, Free Music 2018 also lets you play any songs you have saved on your smartphone. You can also add these to your playlists and favorites without a problem.