Because the guitar has six strings, it is possible to play up to six notes at a time rather than just the three notes in these triads. When you play major and minor chords on the guitar some of the notes of the chord can be doubled up and though the root (the note that gives the chord its name) is the lowest sounding note, the 3rds and 5ths can be played in any order. The order of the notes is often called the voicing.