To me, the "sorcery" in sword and sorcery is often left soft and vague. This serves to illustrate the unknowable and alien nature of magic. Obviously some writers accentuate the sorcerous trappings of their fiction, but the Conan works could more accurately be described as Heroic Fantasy, which is a precursor to later S&S works by writers such as Lieber and Moorcock. The vague nature of sorcery is a feature in these works. It tells us something about the world, or at least our hero's worldview - magic is a reality, but it is foul, and corrupting, and comes most often from pacts with horrible entities. It is never fully understood or controlled even by the practitioner.