At the moment I can't explain it better than this:
"Relations of Production: The objective material relations that exist in any society independently of human consciousness, formed between all people in the process of social production, exchange, and distribution of material wealth." http://www.marxists.org/glossary/terms/r/e.htm
Note that "independently of human consciousness" and that this does not include consumption of material wealth, which to me is where "culture" in the broad sense comes in.