Piano chords or any chord for that matter, are formed by combining two or more scale tones (notes). You now know the tones (notes) that comprise all 12 major scales and you can play these scales smoothly (not necessarily quickly...yet!). It is now time to apply this knowledge and begin combining the scale tones to form chords. You may also see this referred to as combining two or more intervals (remember the definition from your study of major scales). We will begin our study with the simplest and most common type of piano chords, the triad.
As the name implies a triad is composed of 3 notes from the major scale. We shall begin with the major triad. A major triad consists of the 1st, 3rd, and 5th tones (notes) of a major scale. You will also see this referred to as the root (1st), major third (3rd), and perfect fifth (5th). So, based upon this C major chords would
consist of the notes C, E, and G of the C major scale. The symbols for a major triad are Major, M, or Maj. Whenever you see these names or symbols following a piano note (C, D, Eb, F#, etc.) you know it is referring to major triad chords. Or if you are just given the note (C, D, etc.) it is inferred to be a major triad.
Kenneth Larkin
Original source: http://www.articlesbase.com/online-education-articles/learning-the-piano-online-74785.html
