Really, what is joy?

So, as I begin my journey to joy, I've decided that I want to know what joy is? So I'm going to start to research what I can find on joy.

A dear friend sent me these quotes:

"Joy is a net of love by which you can catch souls." (Mother Teresa)

"Joy is the holy fire that keeps our purpose warm and our intelligence aglow." (Helen Keller)

Beautiful...