There are 12 notes on a music scale. They are the based 7 note scale - A, B, C, D, E, F, G, and their transition notes add up to 12.
Sharps and Flats
Flats - Ab, Bb, Db, Eb, Gb
Sharps - A#, C#, D#, F#, G#
Chord
A chord is made up of 3 notes, called a triad.