Eeef...I may be sticking my foot in my mouth somewhat but, here it goes anyway. Refraction is the way light seems to "bend" objects (especially when part of it is placed in water). The Refraction mode will mostly effect stuff that is placed in or under a water plane or volume water. In the geometric view of Bryce the object may look like it is in one place but, when you render it seems to be somewhere (a little left, right, forward or backward). To see a really good example of refraction watch Discovery channel or stuff like that and watch divers go underwater with a camera or the Croc Hunter's camera man when they are tracking something on the water's surface. The more refraction you add the more it will seem to bend or split (if your camera is placed at water level). I hope that was a little clearer than the mud it sounded like. Cheers.