What are Octaves?
This video will help!. Essentially, Octaves are the idea of a same note being 12 semitones higher.
What’s a semi-tone?
A semi-tone is a half step. So a half step from A is A#, and a half-step from G is G#, etc.
Likewise, a whole-tone is a whole step. So a whole step from A is B, and a whole-step from G is A, etc.
Let’s look at a piano:
Notice how there are a bunch of notes – but actually, there are only 12! what happens is that the notes are repeated over and over again. As a result, there are a total of 6 octaves on this piano!