C Major Scale Tones
When constructing chords and scales, we reference the scale tones of the major scale. For example, a "3rd" is the 3rd note in the major scale, while a "b3rd" is the 3rd note in the major scale that is lowered by one-half step.
The easiest example to study and practice initially is the C Major Scale, which has no sharps or flats.
C Major scale
Here is the C Major Scale with the notes notated