Chords are built from scales.

Triads

Triads are chords made with three notes from a scale

The root note gives the chord its name.
A minor or major third
A fifth

Major Triad

Happy

root
Major Third
Perfect Fifth

Minor Triad

Sad

root
Minor Third
Perfect Fifth

Diminished Triad

Tense

root
Minor Third
Diminished Fifth

Augmented Triad

Otherworldly / Dreamy

root
Major Third
Augmented Fifth

Scales

Note that the notation uses upper or lower case and the degrees sign to describe whether the triad is Major, Minor and/or Diminished

Major

Position	Triad	Notation
I	Major	I
2	Minor	ii
3	Minor	iii
4	Major	IV
5	Major	V
6	Minor	vi
7	Diminished	vii°

Voicing

The density of the chord is determined by the proximity of the notes within it. A triad is the densest of chords and the lower down the keyboard, the denser proximate notes sound. By spreading out the notes of a chord, the chord is opened.

Chords