Tonic Notes, Bass Notes and Inverted Chords

Tonic note = note that gives its name to the chord; foundational pitch upon which the chord is built

Bass note = lowest note in the chord

The tonic note will never change and often serves as the bass note in the chord. However, the chord can be built where a note other than the tonic note serves as the bass note. In this case, the chord is an inverted chord.