In OS X there is a lock icon in the lower right of the Get Info screen. What is this icon called? What does clicking this icon do?
Edit: I guess I should add more detail. I am running on an account with administrator access, I have the ability to change permissions of some folders (one on my desktop) but not others (one in the Applications folder). The "lock" is locked in both cases. When I tried to Terminal -> su -> chmod the folder in Applications I still had no luck... until I pressed the 'lock' button.