What does the lock icon on the 'Get Info' screen do?

Question

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?

http://i.stack.imgur.com/XGISB.png

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.

Answer 1

Clicking the lock icon will prompt you for an admin password. After you provide it, the system will allow you to change the permissions for that file or folder in that "Sharing & Permissions" pane you see at the bottom of the Get Info window. This is a feature of the underlying Unix operating system that allows different privileges for a user, group, and others.

There's a reason this feature is "locked" against casual access. It's not really something you want to touch if you're not very sure what you're doing. Messing with permissions can cause access problems, security problems, or both.

For more details, check out this Wikipedia article: http://en.wikipedia.org/wiki/Filesystem_permissions#Traditional_Unix_permissions