Here's a brief crash course in the Library inheritance system.
There are four levels of Library folders:
The first contains things belonging only to Apple and the core of the system. The contents here apply to all users. Users and administrators both should *never* touch what is inside this folder. It should always remain "clean" and safe. In fact, the permissions are set here so that you *can't* modify the contents without explicitly changing the access rights to it first.
The second is only writable by administrative users. Like System, its contents apply to everyone, but if there are ever problems and the system has to be booted into safe mode for repairs, this Library will be ignored and only the known safe items in the System folder will be loaded.
The third is the preferred folder for installing things on a per-user basis. Contents of this folder only apply to the user it belongs to. It too would be ignored in safe mode.
The fourth is rarely used and can be ignored unless you are using a special network setup with Mac OS X Server and a bunch of Mac OS X client machines.
Now, what exactly *do* these three Library folders contain? Good question. There are two basic kinds of things kept here: application settings and application/system add-ons.
By default, an application saves its preferences in the home Library (the "/Users/yourname" one) because, as I explained above, in the hierarchy this one applies only
to the current user. The preference files here are simple text documents and are completely inert. If you delete an app, you can safely leave its preferences file in the Library forever and it will not affect anything until you reinstall that app.
Things that you yourself may place in the Library folders include items such as screen savers, alert sounds, fonts, extra preference panes (for System Preferences), printer drivers, and plug-ins or add-ons for other software. If you browse the contents of the Library folders, you'll see that there are already subdirectories appropriately labeled for some of these things.
Let's consider a couple examples:Q.
You download a new screen saver. You are the administrator of this machine and want to install it so that all users have access to it. Where do you put it?A. /Library
-- more specifically: /Library/Screen SaversQ.
You buy some fonts. You want to install it so that only you can use them. Where do you put them?A. /Users/yourname/Library
-- more specifically: /Users/yourname/Library/Fonts
Does that help?
The Library system seems a little strange at first, but once you understand how it works, I believe you'll come to appreciate it. It's a very logical layout.
Oh, and welcome to AppleInsider! 8) Feel free to ask any more questions. Remember: the only stupid question is the question that goes unasked.