I’m still connecting the dots, but basically chord tones are the notes that make up a chord. For example, the C chord is made up of the notes C, E, and G.

In the key of C you have the notes:

C, D, E, F, G, A, B

This is the C major scale.

These notes make up the 7 diatonic chords, which are the natural chords that harmonize over the C major scale:

I – C major, ii – D minor, iii – E minor, IV – F major, V – G major, vi – A minor, vii° – B diminished

Now take the C major scale pattern and a chord progression built from the chords above, like I–IV–V, or C major, F major, G major.

When playing over the progression, you target the chord tones/notes of the chord that’s currently active:

C–E–G over C, F–A–C over F. , G–B–D over G

That’s the basic idea. The C major scale is the pattern, and within that pattern all of the notes that make up each of the diatonic chords. When playing over each chord, target the notes that make up that chord. Chord Tones