The best way to understand the effect different settings have is to experiment with them. Just do it in a logical way like working your way through the shutter speeds as above.
The try the same with the AV (aperture priority) setting. It doesn't have to be an interesting subject just something that will allow you to see the differences. Place a small object like a cup or similar on the grass photograph it from around 4 or 5 feet away keeping the camera low to the ground. Lying down resting on your elbows should be fine and focus on the cup each time.
Again work through the apertures from one end of the scale to the other. You should see more and more of the grass in front and behind the cup coming into focus on each shot if you work from lower numbered apertures upwards.
Available apertures and shutter speeds vary from camera to camera with the greatest range usually on SLR models.
Common apertures (also known as f.stops)range from f2.8 through f4.8, f5.6, f6.5, f8.0, f11 and more up to as much as f30 or more. The range even on an SLR varies with the lens you're using as the aperture is the size of hole within the lens the light can pass through.
Confusingly the larger the hole (aperture) available the smaller the number that represents it so f2.8 is a larger hole (more light passing through) than f8.0 for example.
You will notice particularly with sports and wildlife photographers that they often have gigantic lenses, this is not only because they are zoom or long focal length lenses but also because to let enough light in the actual glass lenses insidehave to have a large diameter to offer large apertures. This makes them blinkin expensive.
Compare
this with
this, ok the one fixed at 300mm is a much better lens in other respects too but it's the size of the optics in it that allow to go down to f2.8 where the cheaper zoom is stuck at f5.6 at the 300mm end of it's zoom range.
It may not sound much but a bit of extra light through the lens can allow you to user a vital faster shutter speed for fast moving footballers or wildlife.
All automatic cameras measure the available light then balance the aperture and shutter speed to allow a very specific amount through to the film (or CCD in digitals). The speed of the film (50 ISO is not as sensative to light as 400 ISO) so thiss too affects the calculation the camera makes. Digitals sometimes allow you to choose a film speed and similar to film you will see that the faster the film speed the grainier the results will appear.
I've deliberately used 1600 ISO film before to get grainy images.
When you get your head around shutter speeds, apertures, film speeds and how they interact you really can tailor them to control how your images look.
Have I rambled on or was that useful?
