Filesystem Hierarchy Standard
<storage, standard> (FHS) A standard
designed to be used by Unix distribution
developers, package developers, and system implementors.
FHS consists of a set of requirements
and guidelines for file and directory placement under UNIX
-like operating systems.
The guidelines are intended to support interoperability of applications, system administration tools, development tools, and scripts.
These systems should also be supported with greater documentation uniformity.
The standard is primarily intended to be a reference and is not a tutorial on how to manage a Unix filesystem or directory hierarchy.
RedHat deviation (http://www.redhat.com/corp/support/manuals/RHL-6.0-Manual/install-guide/manual/doc084.html).