we could write a whole book on the subject of chord make ups, it's not an easy question to answer in the space of 1 thread, but I'll try to help you out a bit.

All chords have a corresponding scale and vice versa, meaning: all chords come from scales.

Here's a 2 octave C major scale;
C D E F G A B C D E F G A B C
R 2 3 4 5 6 7 8 910 11121314

Chords are built on 3rds, meaning every other note of the scale, or the odd # tones (w/thee exception of the 6th, sus4 and 2)
You at least need 3 notes to have a chord (R 3 5) This is the make up of your standard 3 note chord, known as a Triad. If there is any additional notes added to the chord this information will be supplied within the chord symbol,Cmaj7 ( CEGB)or Cmaj9 (CEGBD)

Here's some common chords and the scales you can associate them with
Major = Major Scale
Minor = Dorian (usually)
Dominant = Mixolydian
Diminished = Diminished
Augmented = wholetone

[Edited by chris mood on 02-22-2002 at 12:05 PM]