What does the little blue light underneath the icons mean?

The small bluish-white light underneath dock icons indicates that the app is currently running. In Mac OS X, the Finder is always running (it's Apple's answer to Windows Explorer). Another difference is that usually, when you click the red X in the top-left corner of a window, it keeps running. To kill the app and free up RAM, press command+Q simultaneously, or choose "Quit" from the application menu near the Apple icon in the top-left corner of your screen, on the menu bar.

You're pretty much right. It just means that app is open, but if you're not going to use that app at all you should completely quit the app by right clicking on the icon and pressing quit (command + q). You should do this so your mac doesn't start to get slow or anything.

HappyUnicorn wrote:

I'm kinda new to mac and so this is very confusing for me. But I think it means that I have visited that app or whatever it's called. Am I correct or totally off?

Hi: Simply means the App is running (Active)

Stedman

Mac 101

http://www.apple.com/support/mac101/

http://www.apple.com/support/switch101/ Switching from PC

If you mean in the Dock, then it means that application is currently running.