One is "Surrounded" and the other is "Free": Pan and Prometheus

Caption NASA:"Two of Saturn's moons coast along the outer edge of the Main Ring System. The orbits of seven small moons cluster just outside the F-Ring -- between the orbits of Pan and the co-orbital moons Janus and Epimetheus.
Pan (approx. 28 Km, or about 17 miles across at its widest point) appears as a bright dot within the Encke Gap, right of center. Janus (about 179 Km, or approx. 111 miles across at its widest point) lies outside the A and F-Rings, below center.

This view looks toward the sunlit side of the rings from about 2° below the Ring-Plane. The image was taken in visible light with the Cassini Spacecraft narrow-angle camera on Aug. 22, 2008. The view was obtained at a distance of approx. 1,3 MKM (such as about 808.000 miles) from Janus.
Image scale is roughly 8 Km (5 miles) per pixel".