Resolution The resolution of an image sensor tells you how many points of light, called pixels it can capture. The higher pixel count you have the better, because this will enable you to enlarge the image without any significant quality loss. Resolution is a very essential factor that affects overall image quality.
Light Sensitivity This is a measure of how much light a digital camera needs to take a perfectly exposed picture. Usually, a camera's light sensitivity is stated as its ISO equivalency. A lower ISO setting produces clean images, but the pictures have the potential to look dark if they are not shot in either bright sunlight or with a good flash. A higher ISO setting can produce better-exposed pictures in low light, but can degrade overall image quality by introducing "electronic noise" to the image itself. Most inexpensive cameras vary automatically between ISO equivalency settings and can't be changed by users.
Lens Speed The amount of light the lens actually lets in is known as its lens "speed". F-stop refers to the unit of measurement that is used to describe the size of a lens diaphragm's aperture. You can find mechanical diaphragms on various digital cameras that can stop down (reduce) the aperture to anywhere from f8 to f11 which produces a greater depth of field.
Focal Length Focal length refers to the amount of distance between the actual lens and the image sensor. You can modify a lens by increasing its focal length which in turn makes objects appear closer and more magnified. If you decrease the focal length, things will appear further away, but it will also widen your viewing field.
Zoom With the zoom feature you have the ability to vary the focal length of the lens to wide angle or to telephoto. When you see a number with an X next to it (i.e. 7X), this refers to the zoom ratio. The X stands for the number of times that the focal length is doubled. The higher the number, the more field coverage you'll get.
Macro This is a special feature that allows you to extend the normal focal range of the camera to take pictures of small items up close. You can capture an object 12 inches away or maybe even close. Most digital cameras come with this feature.
Auxiliary Lens This is a great optional feature that allows you to attach a lens (wide-angle or telephoto) to the front of the camera's primary lens. This feature lets the lens either magnify its subject or increase the viewable area.