Music is made up of three building blocks that continuously interact with each other:
On the piano, melody is most often played in the right hand. It is the most recognizable part of a piece: this is the part that people remember and hum along with.
Melody is often played a little louder than the other parts of the arrangement to make it stand out more.
Melody is also flexible. It can be “distorted” in many ways and still be recognizable as a particular song. Jazz improvisers take advantage of this principle all the time.
Harmony is the chords. On the piano, we play harmony mostly in the left hand, but sometimes we put harmony tones in the right hand as well.
Melody is usually the highest tone and harmony tones are filled in below that. The most important harmony tone is the lowest tone: the bass.
Harmony is also fairly flexible: you can harmonize the same melody in many different ways, although certain chords are easier on the ear than others.
Rhythm keeps music from becoming boring. It’s the thing you can dance to. A drummer plays nothing but rhythm but on the piano we have to put the rhythm into the melody and the harmony.
For us, rhythm is the difference between short tones and long tones, and where you put the accents on those tones.
There you have it. Master those three areas of making music and nothing will be able to stop you! 
