Lens hood?

A lens hood is a cap that protects the camera lens from damage or scratches.

@JA: Wow. That was amazing powers of deduction, right there. Good for you!

It might have something to do with flare?
Not Office Space type flare, mind you.

Yeah, I think it is more like this: http://en.wikipedia.org/wiki/Lens_hood
Not necessarily to protect the lens from scratches, but to act as a shade.

Hey, my answer wasn’t so bad for an edu-ma-guess.

well, i guess it’s also pretty usefull when shooting with a bright flash to keep it from over exposing

@iwamoto, I’ve heard that you shouldn’t use a hood with a flash because it causes shadowing and different amounts of light throughout the picture. A lens hood is to limit the amount of sunlight that hits the lens on a sunny day, therefore you avoid the ‘sunburst’ that comes with really bright sunlight.

it’s used to lessen flaring on the lens in bright sunlight.

if the light is just right and you’re facing the wrong way light will bounce around like nobody’s business in your lens causing bad flaring and you won’t know until afterwards, hoods just keep that extra bit of light from coming in at a large angle and giving some bad flaring.