If we include sharps and flats, there are a total of twelve notes we can produce in music before hitting the same note we started at, an octave higher.
For example, if we started at A we would produce the following notes:
This progression of notes is called a Chromatic scale.
Note: There are no sharps or flats between the note B & C and E & F
Also note that the sharps and flats are the same note - eg. A# is the same as Bb. This is because:
Two notes sharing the same name are called enharmonic. So A# is the enharmonic equivalent of Bb.
On the guitar, one fret = one semitone. So if we fret the guitar in one place and move it up on the same string to the next fret, we will get the next note in the chromatic scale.
Using the chromatic scale, we can work out a complete list of notes on the guitar fingerboard:
At the 12th fret we arrive back at the same note the open string produces, but it will be an octave higher, since there are twelve notes in an octave.
After the 12th fret, the notes will all repeat themselves again in the same order, but will all be an octave higher in pitch.
This diagram is handy to know and should be memorized, as it will make finding notes on the guitar easier. It should be used as a reference at all times until one is familiar with it.