Many fans of Superman always ask, "Where did the 'S' symbol come from?" Throughout Superman's history, there have been a couple of explanations. One explanation is that it was the symbol for the family of El (Superman's Kryptonian family). Another explanation is that it was simply tagged with him by the general public.
I tend to disagree with the later explanation, as he was wearing the logo when he started his crime-fighting career, when he was first relatively unknown.
Though I like the first explanation, and that is the idea that has been adopted by the writers of "Smallville", the comics say that both of these origins are false.
It is said that the "S" logo originates from the Kent family history. The symbol resembles the design of the Iroquios blanked that belonged to Clark Kent's ancestors, Nathaniel and Mary Glenowen-Kent. The "S" of the symbol represents a snake which was then know to represent "healing".
Another question that people tend to ask is whether the costume Superman wears is bullet-proof. As can be found under "Superman's Powers", the suit appears bullet-proof because of the invisible shield surrounding Superman -- a result of the reaction between the earth's sun and his Kryptonian cells. Because the suit is tight against his skin, it appears indestructable. His cape often gets mangled and torn, however as this "shield" does not extend that far beyond his body.