Certifications Mehadrin and Badatz both point to a higher tier of kosher supervision that goes beyond the basic standard. Mehadrin means the agency followed the stricter opinion at each step, and Badatz refers to a rabbinical court whose certification is usually held at that mehadrin level. Neither one means a regular hechsher is unreliable.
Is It Kosher? Yogurt often contains gelatin, and when it does, that gelatin is usually not kosher unless the tub carries a trusted hechsher. Plain yogurt frequently skips it, while flavored and low fat cups are the ones to watch. The label tells you almost everything you need to know.