An anal plug is primarily intended to remain stationary and provide a feeling of fullness/stretch. It’s also meant for use over extended periods of time. Plugs are supposed to be comfortable, but still noticeable. An anal probe is centered more around sensations. They can be used for thrusting or prostate massage, and are commonly vibrating. They’re often longer, narrower, and/or more dramatically textured than plugs. They are not intended to stay in place or be worn around the way that plugs are.