Optical Zoom - Think of it like using binoculars to see something. The quality of the photo you take will remain the same no matter what zoom level you use.

Digital Zoom - Digital zoom is not really zooming in at all, it is just making the photo image larger for when you take it. The quality of the photo will decrease the more you zoom in.

Exposure - This is to do with the amount of light that is aloud to hit the sensor right when the picture is taken.
Overexposure is where the photo that is taken looses detail such as important bright parts of the scene are washed out.
Underexposure is where the shadow of the objects in the photo are very dark.

Shutter Speed - By changing the shutter speed, you can choose how much light you wish to let in to the image when you take the photo. This can be useful for the above reason.

Focus - Focus is perhaps the key thing to consider when taking a photograph. You have to make sure that the camera that you are using is kept still during the actual taking of the picture so that you avoid blurring the picture.
Many cameras have auto focus settings where they will identify the main areas to focus on to give the best photo possible.

Thank you for your input, much appreciated