To answer your question Lynn, what you are talking about is depth of field. Depth of field can be dependent on a number of factors but the main way to get more depth of field is with f-stops which essentially refers to how big the hole in a lens is that lets the light into your camera. The lower the number the f-stop the bigger the hole or aperture. The higher the number the smaller the hole or aperture. Combined with shutter speed, which is the length the time the shutter stays open is where depth of field is born so to speak.
So for simplicity's sake, (which is to say this isn't the whole story) back to the black cat in the coal cellar at midnight. In order to photograph that cat you need a very large (but small number) opening/f stop and a very long shutter speed with a high ASA .. or with the polar polar bear at noon in the snow, a very small (but high number) opening/f stop and a very fast shutter speed with a low ASA.
Here's a link about it all:
http://www.picturecorrect.com/...
