Answer:
A note such as middle C and a C 8 keys above or below it, makes one octave.
To get picky, there are not 8 whole notes to an octave. This is just the old way of doing things that is so popular they haven't got around to updating it. In fact there are 12 notes to what is called a chromatic scale or the current octave: C C# D D# E F F# G G# A A# B