What exactly are b-sides?

[SunshineSlayer]

The term comes from when albums were released on records. One side of it was the A side, then you had to flip it over to play the B side. The term doesn't really apply anymore, since you don't need to flip CDs over. But often times people will use it when describing singles, like fairyland is the A side because it's the main song on the single and alterna is the B side.