For now though, this was just too neat not to share:
It's the pentatonic scale, made up of five notes rather than the seven of the more common diatonic scale. It may not seem that impressive to someone who doesn't have much experience with music, but I know from experience that people generally don't learn music that quickly.
Also, as a fun side note, when I was younger I used to make up music and sing it to myself. I never wrote it out, just sang - composing as I went and forgetting it almost immediately. The vast majority of that music was in the pentatonic scale, not intentionally, but just because it sounded right.