A triad is a three-note chord: a root, a third and a fifth. Build one on every note of the C major scale and you get the seven chords of the key, plus C again at the top. Here they all are on the bass, starting from C on fret 3.
The pattern in any major key is always the same: major, minor, minor, major, major, minor, diminished, then major again at the octave. The Roman numerals number each chord from the scale: capitals for major, small letters for minor, and ° for diminished.
A triad is two thirds stacked on top of each other, the same thirds you played in Exercise 1. The kinds of third decide the kind of chord.
For major chords, play the root, then move to the next string up for the 3rd and the 5th. For minor and diminished chords, the 3rd stays on the root's string and only the 5th moves up a string.
Next string up: 3rd is 1 fret back, 5th is 2 frets forward.
Same string: 3rd is 3 frets up. Next string up: 5th is 2 frets up from the root. Used for Em and Am.
Same string: 3rd is 3 frets up. Next string up: 5th is 1 fret up from the root. The minor shape with the 5th one fret lower.
Tap any note to hear it on its own. All eight triads, climbing from C on the A string (fret 3) to C on the D string (fret 10). C and Dm start on the A string. From Em upwards, every chord starts on the D string. Tap a chord below to pick it out, or play them all.
Tap a note on any card to hear it on its own, or press Play to hear the chord. The "Play chords" switch above sets whether the notes sound one at a time, as an arpeggio, or all together.