Article: A chord is three or more notes. Complex chords may have many notes, but you need a minimum of three.  The chords discussed here will all be composed of three notes: a root, a third and a fifth. Every major chord is built on a note called the tonic, or root of the chord.  This is the note that the chord is named after and will be the lowest note in the chord.  For a C major chord, C is the tonic.  It will be the bottom note of your chord. You will play the tonic note with your thumb in your right hand, or with your pinkie in your left hand. The second note in a major chord is the major third, which gives the chord its character.  It will be four semitones, or half-steps, above the root.  It is called a third because when you play a scale in that key, it will be the third note that you hit.   For a C major chord, E is the third.  It is four half steps above C.  You can count them on your piano (C#, D, D#, E). You will play the third with your middle finger, regardless of which hand you’re using. Try playing the root and the third together, to get a sense of how that interval is supposed to sound. The top note in a major chord is called the fifth because if you play a scale it will be the fifth note that you hit.  It anchors the chord and makes it complete.  It is seven semi-tones above the root.  For a C major chord, G is the fifth.  You can count the seven semi-tones up from the root on your piano. (C#, D, D#, E, F, F#, G.) You play the fifth with your pinkie in your right hand, or your thumb in your left. All notes can be written at least two different ways, for example Eb and D# are the same note.  Therefore, an Eb major chord would sound the same as D# major chord.   The notes Eb, G, Bb create an Eb chord. The notes D#, F𝄪 (F##), A# create a D# Major chord, which sounds exactly like an Eb chord. The two chords are called enharmonic equivalents because they sound exactly the same but are written differently.  A few of the common enharmonic equivalents are noted below, but otherwise the article presents only the most common notation of a major chord.
What is a summary of what this article is about?
Understand what a chord is. Find the root of the chord. Find the major third. Find the fifth. Understand that there are at least two ways to spell a chord.