Competition is normally either zero-sum or positive-sum.
In a zero-sum game, there is a loser for every winner - or more correctly, the total losses are the same as the total winnings. eg if the winner gets a point, someone else loses that point.
In a positive-sum game, there is a net positive win. eg the winner may get 10 points, and the loser may get 5.
Communists, and leftists generally believe that economies are zero-sum. That is, that if you earn a dollar, then someone else is one dollar worse off. If you believe that economies are zero sum, then the communist obsession with distribution of wealth becomes quite logical.
In fact capitalist economies are positive sum - competition and self interest are probably the greatest motivator for efficiency there are.