On most digital cameras you'll see something like P S A M

For my Canon Cybershot DSC H-5 the letters stand for the following:

P - Program Auto - The point and shoot setting

S - Shutter Speed Priority - You set the shutter speed and camera selects the aperture

A - Aperture Priority - You set the Aperture or f-stop and camera selects the shutter speed

M - Manual - You set Shutter Speed and Aperture

Grab your manual and camera and find this feature. I'll be talking about Shutter Speed and Aperture.

Shutter speed is how long light is allowed into the camera

Aperture aka f-stop is how much light is let in

About the slowest shutter speed you can hand hold, even with shaky hand setting is about a 60'th of a second. Anything slower, a tripod is necessary unless you are very young and rock solid.

This is where the fun begins.

Find in your manual where it describes what your display screen shows. By looking at your display screen you can tell what focus mode you are in (usually displayed as a symbol), shutter speed and Aperture (f-stop) along with other things I won't go into yet.

For now, find the area on your display that shows Shutter Speed and Aperture (f-stop) and also find in your manual how to manually set them.

Lets start with Shutter Speed. Set your camera to S mode.

Turn on your camera and point it at lighted area. Now start changing the shutter speeds and watch what happens on your display. Take note of how the Aperture (f-stop) number changes as you change the shutter speed.

Do the same with the Aperture (f-stop). You'll notice how the shutter speed changes with the Aperture settings.

Now put the camera back on P - Program Auto and start moving the camera from light to dark and notice how the two numbers change on Shutter Speed and Aperture (f-stop).

To dive in deeper on these subjects, be sure to check out Dirtdorphin's How I learned about f-stops and Evermorelawnless's Photography 050: Light – ISO, Aperture, and Shutter Speed

The main points to take away from this lesson is first, how to look at your display and see how the camera is set for focus, shutter speed and f-stops and also to see what changing shutter speeds and apertures (f-stop) does to how much light is getting into your camera.

How does the P mode (program auto) differ from the Camera Icon mode (usually auto everything/point-and-shoot) on the Sony? Is there a value being held constant or a variable (or set of variables) that mode appeals to that are different from the Everything Auto mode (camera icon)?

It apparently has a set of variable presets which can be tweaked by the camera for different scenarios like sports which uses a fast shutter or landscape which probably uses a high f-stop or low f-stop for twilight without flash etc. Program auto seems be totally light meter driven. But I'm not 100% sure.

Xeramtheum said: Program auto seems be totally light meter driven. But I'm not 100% sure.

I'll bet that's right. On my K-x in P-mode, it changes the ISO (within the pre-set range), aperture, and shutter speed based on the light meter. In fact, the only value you can mess with on my camera in that mode is the EV (exposure value) setting.

I am pretty sure that's it too because in Program auto I can change Shutter Speed and f-stop and the image in the display remains the same with one or the other compensating for the changes unlike progressive dark to light you get and vice versa when you're in fix shutter or fixed aperture mode.