The C Major scale is one of the most commonly used scales in Western music, and it's also one of the simplest to understand because it contains no sharps or flats. The notes of the C Major scale are C, D, E, F, G, A, and B.

When we harmonize these notes into chords, we get seven different chords that make up the key of C Major. These chords are C Major (C), D Minor (Dm), E Minor (Em), F Major (F), G Major (G7), A Minor (Am), and B Diminished (Bdim).

1. C Major: This chord is made up of the notes C, E, and G. It's the "home" chord in this key, often where songs in C Major will start and finish.
2. D Minor: The second chord in the key of C Major is D Minor, which consists of the notes D, F, and A. It has a melancholic sound compared to the major chords.
3. E Minor: This chord includes the notes E, G, and B. Like the D Minor chord, it has a more somber tone.
4. F Major: The fourth chord, F Major, is made up of the notes F, A, and C. It provides a nice contrast to the minor chords, with a happier sound.
5. G Major (G7): The fifth chord in the key of C Major is typically played as a dominant seventh chord (G7), which includes the notes G, B, D, and F. This chord often creates tension that resolves nicely back to the C Major chord.
6. A Minor: The sixth chord, A Minor, consists of the notes A, C, and E. It shares several notes with the C Major chord, giving it a compatible but slightly sadder sound.
7. B Diminished: The seventh and final chord in the key of C Major is B Diminished, which includes the notes B, D, and F. This chord has a tense, unstable sound, often used to create tension before resolving back to the C Major chord.

These seven chords are the building blocks for many songs in the key of C Major. By combining them in different ways, you can create a wide variety of melodies and harmonies.