Positions on the guitar are determined by what fret your 1st finger is starting on, 1st finger on the 1st fret = 1st pos., 1st finger on the 5th fret = 5th pos. etc. Basically the NOTES of the guitar can be learned in 3 positions, everything else will be an overlap of these 3 pos.

1st position will cover the open strings to the 4th fret. 5th pos. will cover frets 5 - 8. 9th pos. will cover frets 9 - 12.

To figure out where the natural notes are of each position figure out what mode of C exists in each pos. In 1st position E phrygian will be outlined, 5th pos. A aeolian, 9th pos. D dorian.

Once you learn the NOTES of one position you can easily figure out all the others. In 1st pos. we have E F G on the 1st str. In 5th pos. we have E F G on the 3rd str. In 9th pos. we have E F G on the 3rd str. When relating things to 1st pos. you will notice the note groupings for each string remain consistent they just keep moving down one string.

So, yes we do have 12 possible positions on the guitar, I recommend learning the 3 (1st 5th & 9th) and then visualising the other 9 pos as an overlap of these 3.