Aperture is in the lens itself, it's a diaphram that opens and closes to control the amount of light coming into the camera. It's also commonly called the f-stop.Originally Posted by MaorG
The aperture controls the amount of light coming through the lens. Your shutter speed controls how long the film (or in the case of digital, the sensor) is exposed to the light.
Your shutter speed and aperture work together to control the exposure.
But each one has different effects depending on how they're set. Shutter speed settings allow you to blur or stop motion. Aperture controls your depth of field (DOF).
Depth of field will control how much of the image can be sharp. The wider the aperture, the more shallow the DOF will be. If you want as much of the image as possible to be sharp, then you want a narrow aperture. If you want just a single subject in focus with the background blurred out, you want to use a wide aperture.