Complex sentence: It is usually Orthodox rabbis who assume the jobs of "mashgichim" (singular: "mashgiach", "supervisor"), meaning they "supervise" the products and processes that manufacture kosher food to ensure compliance with the required standards.
Split into simpler sentences: It is usually Orthodox rabbis who assume the jobs of "mashgichim" (singular: "mashgiach", "supervisor"). This means that they will "supervise" the products and processes that manufacture kosher food to ensure compliance with the required standards.