Major chords are the most used type of chords in today's popular music, carrying an hopeful, upbeat, full sound.
The C major guitar chord's notes: 1(C) - 3(E) - 5(G)
C Major chord's recommended scales: major scale, lydian scale and the pentatonic major scale. As you can notice, the C major scale is the only major scale that has no flats or sharps: C, D, E, F, G, A and B.
Minor chords are more intimate sounding than the major chords, expressing desire, sadness, mystery...
The C minor guitar chord's notes: 1(C) - b3(Eb) - 5(G)
C minor chord's recommended scales: Pentatonic Minor scale, Blues scale, Phrygian scale, Aeolian scale and the Dorian scale.
Jazz and country guitarists use the 7th chords very often. The chord sounds a little bit twangy, not as uplifting as the major chord.
The C 7th guitar chord's notes: 1(C) - 3(E) - 5(G) - b7(Bb)
C7 chord's recommended scale: Mixolydian scale.
Diminished chords are unstable chords, sound very dissonant, like they lack something (usually the major chord a half step up from that diminished chord). For example, a C diminished chord would naturally want to lead into a C# major chord.
There are three different kinds of diminished chords: diminished triad, fully diminished 7th and the half diminished 7th.
The C diminished triad guitar chord's notes: 1(C) - b3(Eb) - b5(Gb). Cdim chord's recommended scale: Whole Diminished scale.
The C fully diminished 7th guitar chord's notes: 1(C) - b3(Eb) - b5(Gb) - bb7(A)(or a 6. interval).
Cdim7 chord's recommended scale: Whole Diminished scale.
The C half diminished minor 7th guitar chord's notes: 1(C) - b3(Eb) - b5(Gb) - b7(Bb). Recommended scales: Locrian scale and Half Diminished scale.
C minor 7th on fret 3, C major 7b5 on 10.fret, C2, Csus2, Csus4, C7sus4, C6 chord, C9 (6.fret) v.2, Cm9 chord, Cmaj9, Cadd9, Cadd9 (8.fret), Cadd9(no3), C6/9 chord, C7-9 (8.fret), Caug chord, C+5 chord, C7+5 chord, C-5 on fret 7, C7-5, C9-5 chord, C11 chord and C13 (5.fret).