When taking photos, your camera needs to be exposed properly and in focus. Exposure is how much light is getting into your photo, and can be set by shutter speed. Focus is how clear your point of main focus is, and can be set by changing the aperture (front of the camera's lens)

Here's a picture of the basic settings on some Canon Cameras you may be familiar with.

The P setting is Program mode. This has the camera calculate both shutter speed and aperture. Exposure becomes automatic, while shooting mode, flash, etc can be set manually still.

The AUTO means that these setting automatically change your camera for various things.

The head is Portrait Mode. This widens the aperture, throwing the background out of focus so that your camera may focus in on someone's face.

The hills is Landscape Mode. This sets a small aperture, allowing a depth of field. On some cameras, flash may be deactivated.