Karl Marx proposed a theory of history in which society apparently progresses through definite stages. The catalyst for change from one stage to the next is a tension between the productive forces (PF) and the productive relations (PR). At least, this is how some have interpreted Marx’s theory.
According to this model, the PR are the social aspects of production in a given society, usually the legal or brute force means of exploiting labor, extracting surplus and maintaining social dominance of the few over the many.
By way of contrast, the PF refers to how a society actually produces commodities.
There is some feedback from the PR to the PF. But the PF determine the PR because the PF are more fundamental to society. In short, the social (PR) depends on the material (PF). And the material (PF) is primary to capital.
I wrote a paper about this back in 1985. The wording is a bit laborious. I was a relatively new university student perfecting a formula for getting good marks, so maybe I was subconsciously mimicking my professor. Over the years I found that grades were usually higher when you wrote like your professors spoke, which was sorta sad but true.
Despite the old-world sentences, the content is good. So I refer you to that for more detailed coverage, especially pp. 2-4: