Major Triads: These consist of the root, third, and fifth notes of a major scale. For example, the major triad for the key of C major would be C, E, and G. Major triads always sound harmonious and bright.
Minor Triads: These consist of the root, flattened third (also called the "minor third"), and fifth notes of a minor scale. For example, the minor triad for the key of A minor would be A, C, and E. Minor triads have a more sombre, melancholic sound than major triads.
Dominant Seventh Chords: These consist of the root, third, fifth, and flattened seventh notes of a scale. For example, the dominant seventh chord for the key of G major would be G, B, D, and F. Dominant seventh chords are often used to create a sense of tension or excitement in music.
Susp4 Chords: These consist of the root, fourth and sometimes the fifth notes of a scale. For example, the sus4 chord for the key of C major would be C, F and sometimes G. Susp4 chords have a more open and airy sound than other types of chords.
Diminished Chords: These consist of the root, flattened third, and flattened fifth of a scale. For example, the diminished chord for the key of B flat minor would be B flat, D flat, and F. Diminished chords have a dissonant, dark sound and are often used to create a sense of suspense or mystery in music.
Augmented chords: These consist of the root, third, and sharpened fifth (also called the "augmented fifth") notes of a scale. For example, the augmented chord for the key of F major would be F, A, and C#. Augmented chords have a bright, piercing sound and are often used to create a sense of urgency or excitement in music.
These are just a few examples of the many different types of chord combinations that sound good together. Ultimately, the best way to learn what sounds good together is to experiment and play around with different note combinations until you find the ones that you like the most.