Though there are competing theories about the formation of the planets, including Saturn, the most widely accepted theory in 2014 is that of core accretion. Gravity pulled elements in space together in clumps. The clump cores then rotated, binding gases and other elements.
Saturn did not form a terrestrial surface because it pulled gases close to its core without high solar winds to sweep the gases away as in the formation of the inner planets. Saturn formed relatively quickly to stabilize the gases around its core. The rings around Saturn formed as comets, asteroids and other space objects disintegrated within the planet's gravitational orbit.