what is the difference between capitalism and communism ?

Capitalism is a market based economy.  'The market' makes the decisions--that is, people who buy things decide which companies prosper and which go out of business.

Communism is a 'command economy', meaning the govt. decides what will be made, how much, and what the price will be.

Capitalism depends on private enterprise, that is investors putting money together to go into business, make a product, provide a service, etc.  They RISK their money in hopes of making a profit.

Under communism all 'means of production'--that is factories, mills, farms, lumber forests, mines, etc.--are publicly-owned and run, for the people's benefit, by the govt.

But PURE capitalism or communism have never really existed.  The US is a 'capitalist-themed' economy, but private corporations get a lot of govt. help.  And all the countries that have declared themselves communist have never even come very close. They were all just corrupt dictatorships all along.

Capitalism is a type of economy in which private ownership exists and distribution of resources occurs by a system of supply and demand that is guided by the collective choices of suppliers and demanders, or what Adam Smith refers to as "the invisible hand." Communism isn't just a type of economy but is also a type of government, the two going hand-in-hand to form a system in which private ownership does not exist and distribution of resources occurs by way of bureaucratic systems in government. 

I can't dumb it down any more than that. That is as poor as words can go to describe the difference. If you cannot understand this explanation, then you are too poor in education to understand any explanation.