It's meant as "black and white" then "exposure brush", I'm pretty sure CS3 doesn't have it, but I know CS4 does.
Basically, it lets you "paint" adjustments if you only want them in one specific area (for example, the eyes slightly more exposed than the rest of the photograph). If you had the time or patience, you could make it two different layers and "erase" the eyes in the top one so they show through.
She has great coloring in her eyes to begin with, so go easy on them
Hope that helps.