|TriadsThe three notes at the bottom of every chord are called a triad. In fact any chord without numbers in its name is only a triad. A triad consists of a root, a third, and a fifth (1-3-5, Do-Mi-Sol).|
Triads have been the chord of choice to end music since about 1500. Before that the term open triad referred to a root-fifth-octave chord. The open triad refers to the fact that the third is missing. This chord was the ending that the modern major and minor triads replaced. Do not confuse open triad with the term open harmony.