Like intervals, triads can be inverted by moving the lowest note up an octave.
The lowest note, called the bass note, determines the name of the inversion.
When the lowest note is the root of the chord, the triad is in root position.
Next, let's invert the chord. The bass note is now the third of the chord. This is called first inversion.
Let's invert the chord again.
Now, the fifth is the lowest note of the chord. This is called second inversion.
Let's invert the chord one more time. Notice that the triad returns to root position.
Use this chart for reference to triad inversion.