Have you ever tried to listen intently to a guitar piece trying to figure out how many are playing? In classical guitar, it is common that there are duos and trios, but certain pieces are composed to sound like more than one guitar is playing.
In electric guitar playing, however, you can play most pieces you already know and make it sound like at least two are playing at the same time. Yes, first time I heard of it, too. With a 12-string guitar, that is how it sounds.