what is life?

I don't know really about what is living life. When i read <What men live by> by Neo Tolstoy , it made me realize that men live by love.

But do we really live only by love? what else? what about fame? and also wealth? and human relationship without love? 

If homeless men with no penny but much love is truly happy? I don't know what is proper answer for it. 

Time flies so fast and it makes me confused more and more.