Ubuntu and System Domains

[Brett Kirksey]

Since OS X was the first unix I ever used on a regular basis,
I've assumed one of its features is common to all *nix flavors,
but I haven't seen any mention of it here. Is Ubuntu divided
into "domains" the way OS X is?

For example, in OS X most of your configuration type files are
kept in a directory called "Library". Any time the system needs
something from the Library, it will look in the System
directory's "Library" (System Domain), the root directory's
"Library" (Local Domain), and the user's "Library" (User
Domain). A user can then install fonts, utilities, etc. that are
only available to them and not polute the system with their
add-ons. This same principle applies to Applications, Documents,
etc.

I see this basic prinicple applied in Ubuntu/Linux by having
similar directories in "/", "/usr", and "/usr/local". But does
this also apply to the home directory?

Can Ubuntu properly locate items installed in the user domain
without specifically being told to do so?

Thanks,
Brett