Never heard of it before. Do you know what an octave is? 12 half steps higher then the original note. An octave of B will vibrate 2x as fast as B resulting in the same pitch. For E played on open E the octave can be found on the 12th fret. The octave of a root note open E power chord is played with the root note on the 12th fret, and the conforming power chord shape. I assume that this is an example of an octave chord.