We'll look at the major Scale. The Major Scale is great for Major Chords; such as Major 7 chords, Major 9 chords, major 13 chords, etc.
The Major Scale is made from a series of Whole and Half steps, which can be directly connected to the piano keys. one key to the next key is a half step. One key to another, skipping on e in the middle, is a half step...
C major Scale:C D E F G A B C D E F G A B C
To figure it out from a series of whole and half steps, you would do this:
From C-D is whole step, D-E whole, E-F half, F-G whole, G-A whole, A-B whole, B-C is half.Or,
simply known as W W H W W W H.
So, to make a D major scale, you would use the series of whole and half steps and a picture of the piano keyboard in your head.
W W H W W W H= D E F# G A B C# D