Karl Marx was a 19th century German philosopher whose ideas formed the basis of communism and significantly influenced the fields of economics and commerce. Some of Marx's key contributions included critiquing capitalism and private property, advocating for proletarian revolution, developing theories of surplus value, wage determination, and the labor theory of value. Marx analyzed how capitalism exploits workers and pushes wages down over time as profits rise, laying the foundation for communist and socialist movements that sought to redistribute wealth more evenly.