You can change the resolution on your screen to anything below the native resolution. For the 17" that is 1920x1200 pixels, you can change it to the steps below that, like 1440x900 (the resolution on the standard 15").
Resolution Independence is a feature that makes objects on the screen 'scalable'. So instead of changing the native resolution of your LCD to something smaller (by smaller I mean a lower resolution, which isn't ideal), you can increase the scale of the ALL the objects on the screen. So if you made it 1.25x scale on the 17" you'd would have the effect of lowering the resolution to 1440x900, but without the blurriness associated with using an LCD not at it's native resolution.
Um...I hope that makes sense.