Puede escribir "man hier" para obtener información sobre el sistema de archivos. Desde la página del manual:
NAME
hier -- layout of filesystems
DESCRIPTION
A historical sketch of the filesystem hierarchy. The modern OS X
filesystem is documented in the ''File System Programming Guide'' avail-
able on Apple Developer.
[omitted]
/var/ multi-purpose log, temporary, transient, and spool files
at/ timed command scheduling files; see at(1)
backups/ misc. backup files
db/ misc. automatically generated system-specific database files
log/ misc. system log files
mail/ user mailbox files
run/ system information files describing various info about system since it
was booted
utmpx database of current users; see utmpx(5)
rwho/ rwho data files; see rwhod(8), rwho(1), and ruptime(1)
spool/ misc. printer and mail system spooling directories
mqueue/ undelivered mail queue; see sendmail(8)
tmp/ temporary files that are kept between system reboots
folders/ per-user temporary files and caches
...