Auto mode tells your camera to use it’s best judgement to select shutter speed, aperture, ISO, white balance, focus and flash to take the best shot that it can.
When you switch to portrait mode your camera will automatically select a large aperture (small number) which helps to keep your background out of focus (ie it sets a narrow depth of field – ensuring your subject is the only thing in focus and is therefore the center of attention in the shot).
Macro mode lets you move your closer into your subject to take a close up picture. It’s great for shooting flowers, insects or other small objects.
Landscape mode is almost the exact opposite of portrait mode in that it sets the camera up with a small aperture (large number) to make sure as much of the scene you’re photographing will be in focus as possible (ie it give you a large depth of field).
Sports Mode is ideal for photographing any moving objects including people playing sports, pets, cars, wildlife etc. Sports mode attempts to freeze the action by increasing the shutter speed.
Night mode (a technique also called ‘slow shutter sync’) is for shooting in low light situations and sets your camera to use a longer shutter speed to help capture details of the background but it also fires off a flash to illuminate the foreground (and subject).
Movie mode extends your digital camera from just capturing still images to capturing moving ones.
Aperture priority mode is useful when you’re looking to control the depth of field in a shot (usually a stationary object where you don’t need to control shutter speed).
Shutter priority is very similar to aperture priority mode but is the mode where you select a shutter speed and the camera then chooses all of the other settings.
Program mode is similar to Auto but gives you a little more control over some other features including flash, white balance, ISO etc.
Manuel mode you have full control over your camera and need to think about all settings including shutter speed, aperture, ISO, white balance, flash etc.