Chord is a harmonic set of at least three tones.
The most used chords are triads. Triads are constructed from two thirds placed one on top of the other. This way we get a set of root tone, third and fifth. E.g. major triad consisting of major third (lower) and minor third (upper) includes root tone, major third and perfect fifth:
There are 4 types of triads:
By shifting the lowest tone one octave higher we create a chord inversion. After first shifting (of root note) we get first inversion. After second shifting (of third) we get second inversion:
Practice chords in our
chord identification online exercises.