The Filesystem Hierarchy Standard (FHS) is a definition of standards for Unix (and hence Linux) directories for the organisation of the files in a working system.
- http://www.pathname.com/fhs/ describes version 2.3 not updated since 2004.
- http://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard
To quote from http://www.faqs.org/docs/gazette/paths.html
The FHS is a subset of the LinuxStandardBase (LSB), which promotes a set of standards to increase compatibility among Linux distributions and enable software applications to run on any compliant system.
See also UbuntuLinux, SixtyFourBitLinux, IntelSixtyFourBitLinux