Who is karl marx, the background? what does he do and why does he do it?

Karl Marx was a German philosopher and revolutionary socialist Karl Marx published The Communist Manifesto and Das Kapital, anticapitalist works that form the basis of Marxism. 

Marxism is the political and economic theories of Karl Marx and Friedrich Engels, later developed by their followers to form the basis for the theory and practice of communism.

The answer is crop yield.