I always asked myself about their main differences. I mean why do I need Ethereum if there is Bitcoin ? I knew about smart contracts running on Etherum but I didn't know much about them.
Then I read an article on HuffingtonPost. It was the best reading I had in the last two months.
Here you find it.
http://www.huffingtonpost.co.uk/quora-uk/how-is-ethereum-different_b_17999462.html?lipi=urn%3Ali%3Apage%3Ad_flagship3_feed%3BNqdyreUKQ8qxzNKBgamZCg%3D%3D
Enjoy reading :-)