Most scales contain seven notes.
You already know at least one: the major scale (“Doe a Deer a Female Deer, Ray a drop of golden Sun” and other horrible, upbeat songs)
In the key of G the major scale would contain these notes:
|2||2||1||2||2||2||1||nr. of frets up|
It’s called a major scale because it contains a major third.
This ‘third’ is the interval (meaning distance) between the tonic and the third note of the scale, in this case a G and a B.
This interval is 4 frets and sounds upbeat.
Every scale that has this formula (2,2,1,2,2,2,1) of frets between notes is a major scale.
As you can see, a scale is nothing more than a bunch of notes lined up with a certain formula of intervals.
|G||–||A||Major Second||2 frets|
|G||–||B||Major Third||4 frets|
|G||–||C||(Perfect) Fourth||5 frets|
|G||–||D||(Perfect) Fifth||7 frets|
|G||–||E||Major Sixth||9 frets|
|G||–||F#||Major Seventh||11 frets|
If you continue to play the scale up from the octave, you’ll encounter these intervals:
|G||–||A||Major Ninth||14 frets|
|G||–||E||Major Thirteenth||21 frets|