@Scrbblechick -- I'd say it's a safe bet that the soy sauce we usually find is the light kind.
When I think of "light" soy sauce, I usually think of the lower sodium kind. Kikkoman makes a great low-sodium soy sauce that I use all the time. I like it because the lower sodium content allows the other flavors to come through. I've seen other low-sodium varieties and I think they're becoming more popular as more people are watching their sodium intake for health reasons.