A triad is said to be in inversion when some note other than the root is in the bass. When the third is in the bass, the triad is in (first inversion); when the fifth is in the bass, the triad is in second inversion. Therefore, there are three possible triads, i.e., root position, first position and second position (there are more possible but I'll stick to basics, figured bass blah blah blah).
Chord in inversion are found in musical compositions for two reasons.
- To give variety to the vertical sound. A composition consisting of the chords with root in the bass only is less interesting musically than alternation of chords with root in the bass and chords in inversion.
- To allow the bass line to be more melodic. Use of inversion allows more step-wise movement and smaller skips in the bass line.
Root pos. > Root example = C
1st inversion > 3rd >>>>>>>>> E
2nd inversion > 5th>>>>>>>>>>G
First inversion of the example above =
Second inversion =
A great musician once told me, learn all the rules and then forget them. This is just one of the tools in a huge bag of tricks that some people call rules or music theory. But don't get overwhelmed, my use of the term "rule" does not imply strict adherence. I use rule in the same sense as when one says, "as a rule, the bus is usually late." I hope this helps you add some diversity to your playing and isn't too confusing!