You will also find out that, depending on each person's playing style and musical tastes, they use fifths differently. Here are some examples.
For instance, a fifth tone is "implied" in any root. So many pianists, if they are playing the root, will not play a fifth. Some pianists, however, use fifths and say that it makes their octaves sound fuller in the left hand. It is all a matter of taste and preference.
In the upper registers, if you play an octave, playing a fifth will make those octaves "scream" a bit more. So if you are high on the keyboard, playing a C-G-C with your right hand makes it stand out a bit more than playing a C-C octave. Same with a Eb-Bb-Eb as opposed to an Eb-Eb. Try it and see if you hear a difference.
The defining tones in your right hand are often the third and the seventh of whatever chord you are playing. This is because, like I said before, the ear "hears" a fifth in almost every root.
Fifths can be useful in giving a different kind of bass than an octave. For instance, play something in your right hand in the key of F. Now play it over an F-F octave in your left hand. Now play the same thing over an F-C perfect fifth in your left hand. Hear the difference?
Everyone will come to their own preference of how to use fifths, if they hardly use them at all. Experiment and come up with your own taste.
Hope this helps some.
Be Blessed
