A chord is a simultaneous sounding of more than 2 notes. Each quality triad contains a unique set of intervals.
Triads occur in root position, first and second inversion.
A triad is said to be in root position when all the intervals are types of thirds. In this case, the bottom note is called the root. Each quality triad may occur in first inversion. In first inversion all triads will contain the interval of a 3rd and a 6th above the bass. The quality of the 3rds and 6ths will be different for each quality of chord.