OSX Dialog boxes, glowing buttons?

This might be a stupid question, but i am new to the OSX environment.

I'm wondering.... when presented with a dialog box there are sometimes some buttons which are highlighted, some are outlined and some are not lit up. What does this designate? What i mean is, when i see a dialog box with a button that is full blue, that means its the default button right? When i hit enter, that is the option that is triggered. What does an outlined button designate?

For example. When i hit the power button (the hard button, not via menu option) i get this dialog box:



Shut down is the default when i hit return, but what is restart? When i hit ESC it triggers cancel. What does the outlined button mean???

that makes sense

ahhh.... that makes sense, its like the dotted outline in windows. Thank you. And thanks for a quick response.