The Program Mode is typically indicated with a “P” on the shooting mode dial. This shooting option on your camera is one of the more simple modes to use as the camera calculates a suitable shutter speed and aperture setting for you. The only setting the user changes is the ISO (sensitivity).
The following video below shows changes the camera makes when the user changes ISO values while using Program Mode. Although Program shooting mode makes taking a quick image easy, it does not allow for much customization if lighting is poor, or does not allow for setting aperture or shutter speed to capture a desired image if you’re looking for creative backgrounds, long exposures, or stop action.
In this mode your camera will try to select a shutter speed that allows you to hand-hold your camera (i.e. no tripod), however if light is low your camera will possibly not select a fast enough shutter speed to stop the action. You may have to adjust the ISO setting higher (in low light) to gain a faster shutter speed. Its also possible your camera will not take the image if light is too low.
If you need a blurred background as in a portrait photograph, the camera might not select a wide enough aperture to create a nice background.
If you need to catch a quick shot before the scene changes, though (e.g. a child doing something cute) using your camera in Program Mode with enough available light will usually take a good exposure.
[youtube https://www.youtube.com/watch?v=neQxX86koa0&w=420&h=315]