What is a safelight, and what is it for?
A filtered light source which allows you to see without fogging your film or paper. Black&White paper is not sensitive to certain wavelengths of light, so you can have some light in your darkroom (enough to see) without damaging the paper. Negatives are sensitive to just about all light, so you can’t use a safelight with negatives (except for orthochromatic films, which you just about can’t find anymore anyway). Color paper, also is less sensitive to certain wavelengths of light, so you can have some light in the darkroom. However the safelights for color are different, and significantly darker than for black&white. Kodak’s black&white safelight is called OC, here is a page on building a safelight.
