ISO, Aperture, & Shutter Speed

These three components of photography are also known as the exposure triangle. These are the three elements that you will have to change on your camera in order to get a perfectly exposed photograph. You will ALWAYS be changing your aperture and shutter speed in order to get the photograph you want (i.e. I want a photo with movement, I want a photo with blur, I want to capture sports action, I want a great portrait, etc.). Your shutter speed and aperture will give you the specific results you want. So what the heck are these things?

• ISO – the level of sensitivity of your camera to available light. It is typically measured in numbers, a lower number representing lower sensitivity to available light, while higher numbers mean more sensitivity. More sensitivity comes at the cost though, as the ISO increases, so does the grain/noise in the images. ISO values: 100, 200, 400, 800, 1600.
• Shutter speed – the length of time a camera shutter opens to allow light to expose onto the film or camera sensor. Shutter speeds are typically measured in fractions of a second, when they are under a second. Slow shutter speeds allow more light into the camera sensor and are used for low-light and night photography, while fast shutter speeds help to freeze motion. Shutter Speed values: 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000
• Aperture or F-stop– the opening within a lens, through which light travels into the camera body. The larger the opening, the more light passes to the camera sensor. Aperture also controls the depth of field, which is the portion of a scene that appears to be sharp. If the aperture is very small, the depth of field is large, while if the aperture is large, the depth of field is small. In photography, aperture is typically expressed in “f” numbers (also known as “focal ratio”, since the f-number is the ratio of the diameter of the lens aperture to the length of the lens). Aperture (f-stop) values : 1.7, 2.8, 4, 5.6, 8, 11, 16, 22 

Read more: http://photographylife.com/iso-shutter-speed-and-aperture-for-beginners#ixzz3DlHL7ZCJ 

Shallow depth of field is when one part of the image is in focus and the other is not and happens with a wide-open aperture (f/2.8 or lower).

Here's an example of bokeh - the out of focus area in a shallow depth of field image, usually referring to lights at night or sunlight through trees. 

Landscape photography uses a higher aperture (f/22 or higher) to create a focused image from foreground to background.

Same scene with totally different effects based on camera settings.