There are many differences between these socioeconomic systems, both in theory and as they’ve been practiced in history. The first and biggest one is there in the names:
communism is focused on commonality; its economics is based in shared ownership of what Karl Marx, its greatest theorist, called “the means of production.”
capitalism is focused on control and concentration of capital, most especially the cash used to create and operate businesses, including hiring workers.
Communism as Marx described it has never yet been practiced on a national scale.