A simple explanation is B-corps can have a charter which is at odds with the interests of shareholders while C-corps are fully aligned with 'maximizing shareholder value'

e.g. "I've created a B-corp, named Betsy, which has the distinct mission of making it viable for more people to choose craftsmanship as a career. I cannot be sued for adhering to my charter in good faith so one thing I can offer all sellers is an insurance plan even if this move has a net negative impact on profit."

This can be contrasted to a C-corp in which its officers could technically be sued by acting in ways which are value or profit-destroying for the firm.