Maximum Aperture
Why should you care what the maximum aperture is?
Simple, the maximum aperture decides how much
light your camera lets in to record the picture.
The larger it is, the more light gets in, thus
allowing you to shoot in a bigger range of lighting
situations. With a large enough aperture, you
could shoot on a cloudy day without the use
of flash; you could shoot action pictures using
a fast shutter speed; you could shoot portraits
and throw the background out of focus.
If the maximum aperture is small to start out with, you can only shoot in a limited range of lighting situations, and would be overly relying on the flash to provide enough light to properly expose your shots. And more often than not, the camera flash is pretty weak and useful mainly as fill-in flash. You would be using slow shutter speeds which means that action shots without flash would be impossible. Slow shutter speeds also mean that any movement on your part (i.e. camera shake) results in blurred pictures.
Some digital cameras have a limited aperture range. Instead of an iris that opens (larger aperture, more light gets in and less depth of field) and closes (smaller aperture, less light gets in and more depth of field) in increments, they might have only 2 preset aperture settings. In fact, some might not have an iris at all, which means that you cannot really control depth of field. The aperture might be "electronically controlled" by moving a filter into the light path to cut off the amount of light reaching the image sensor; this, in effect, simulates a smaller aperture setting but depth of field is not affected. Is this good or bad? Well, the jury is still out on this one. Technically, 2 preset apertures with no ability to control depth of field is a limiting factor for those who want to explore digital photography, but if such a camera takes superb pictures, and you're just interested in point-and-shoot, then who is to complain? Keep an open mind, and don't judge a digital camera only by its features -- it's the picture quality that counts in the final analysis.
