ISO Exposure, Shutter Speed, Aperture

I think its important to mention in few words the meaning of the above words,their understanding helps a good deal when using a DSLR camera.

ISO- measures the sensitivity of the image sensor. The lower the number the less sensitive camera is to light and the finer the grain. Higher ISO settings are generally used in darker situations to get faster shutter speeds (for example an indoor sports event when you want to freeze the action in lower light) – however the cost is noisier shots.

Exposure- the amount, controlled by aperture and shutter speed, that reaches the image sensor.
A correctly exposed image its a file that shows a full range of tones, from deep shadows to bright highlights, with details across the entire image.

Shutter speed - its the measure of tue duration or lenght of the time that the shutter stays open. The longer the shutter stays open the more light will be allowed to reach the image sensor. Faster the shutter speed "freeze" the action and often require more light and a larger aperture.Slower the shutter speed enable pictures to be taken in lower light with smaller aperture.

F-stops(Aperture) -The amount of the light hitting the sensor is controlled by the aperture in the lens. As the aperture is opened and closed it is given a numerical value called the F-stop
The larger the F-stop number the smaller the aperture.The smaller the F-Stop number the larger the aperture and the more light the lens will let through to the image sensor.
Aperture and depth of field - The adjustable size aperture in your lens has an effect in how much of your picture appears sharply focused. The smaller the diameter of the hole(large F-stop number), the greater the range of the items,at distances closer or further away,that will appear sharply focused (along with the specific subject that you actually focused on)
A photograph with objects spread over a wide range of distances,where all are clearly focused,is said to have a large depth of field.
The opposite to large depth of field (small or shallow depth of field) is created when you photograph a scene an aperture with a large-diameter hole (small f-stop number).
These images generally have a single object sharply focused, with he rest of the image blurry or unsharp.

Info from
National Geographic Photography basics:"ultimate field guide to photography"
Creative use of camera controls- leaflet.