Pose is usually a certain position or still shot of someone. Like posing for a picture or a model posing on the runway. Usually yoga pose is the term used as well (not yoga posture).
Posture refers to having good body position. Usually back straight as opposed to being hunched over. Yoga posture refers more to having good form instead of the shape the body is in.
Pose: body position
Posture: how good or bad that body position is
Hope that helps!