what's this?

On my wired keyboard, it says clear. Try selecting some text and pressing it. Unlike the delete keys, it does not delete characters before or after the cursor, but only when text is selected. I'm unsure if it has any uses besides clearing text though. I've never used it before.

 

"clear"

From wiki - "A Clear key, instead of a Num Lock key, on models with full numeric keypads, as these are dedicated to numerals and not generally used for cursor control."

http://en.wikipedia.org/wiki/Apple_Keyboard

 

Sweet! I just realized that in calculator (both application and widget), you can use it as an actual clear key too... Much easier than having to use escape as I have always been doing.

 

Can't help you with that one. That button's missing entirely from my keyboard. Instead, there's a function ("fn") button.