Communism

Can anyone succinctly explain communism? Everything I've read in the past said that the state owns the means of production and in practice (in real life) that seems to be the reality. However I encountered a random idiot on the Internet that claimed in communism, there is no state and it is a stateless society. I immediately rejected this idea because it was counter to what I knew about communism irl. In searching using these keywords, I came across the ideas that in communism, it does strive to be a stateless society. So which one is it? If it's supposed to be a stateless society, why are all real-life forms of communism authoritarian in nature?