Chord structures

Name	relative intervals	example in C
-- basic chords --
maj	0 - 2 - 1.5	C - E - G
min	0 - 1.5 - 2	C - Eb - G
dim	0 - 1.5 - 1.5 - 1.5	C - Eb - Gb - A
aug	0 - 2 - 2	C - E - G#
-- a few variations --
6th	0 - 2 - 1.5 - 1 (major+6)	C - E - G - A
7th	0 - 2 - 1.5 - 1.5 (major+7)	C - E - G - A#
maj7th	0 - 2 - 1.5 - 2 (major+7.5)	C - E - G - B
min7th	0 - 1.5 - 2 - 1.5 (minor+7)	C - Eb - G - A#

• maj = major -- the most common chord-type. Sounds "open" and "happy".
• min = minor -- next most common. Sounds "sad".
• dim = diminished. Like a minor chord with the top note lowered a half-step, leaving room for a 4th note. "Spooky". Often used for transitions.
• aug = augmented. Like a major chord with the top note raised a half-step.

You can combine some of these, like "major augmented 6th" but there are conventions which sometimes come into play (e.g. "major 7th" is not a major plus a 7th, and it should be called a "major seven-and-a-halfth" but it isn't) so it's usually simpler just to give the basic chord and then describe the alterations.