I did some renders to better give kawecki an idea of what the terms mean

Things to note:

1. In the shadows scene, note how the shadows properly blur with angle and distance. And how the color from the surrounding seeps into them. Both are things you can't easily do without raytraced shadows and they add greatly to the look of a scene.

2. The subtle color variations in the cubes come directly from the IBL. This is also very important as it makes your scene look vibrant and rich. It also gives it nice lighting.

3. In the AO scene, notice how 'solid' the scene looks, even though it is just a bunch of blank white cubes. That's how important contact shadows are.

4. In the SSS one, note how it respects the thickness of the object. and casts internal shadows (like on the base) Both are not easy to fake.

EDIT : Just thought I'd add that this is XSI, not poser in case anyone was wondering. Poser as yet doesn't support some of this stuff, mores the pity. You can do AO and IBL. of course.