for the curious reader,
sbin is short for “system binaries” (although it’s sometimes been described as being short for “static binaries”, because on some systems the executables in
/sbin would always be statically-linked to ensure a bootable system if
/lib was destroyed);
lib, fairly obviously, stands for “libraries”.
/var contains “variable files” — things like logs, process IDs, temporary directories, mail spools.
/proc (on systems which have a
proc filesystem) originally just contained information about running processes, but Linux extended this to include lots of other information, too (for example,
On some older Unix variants,
/etc often contained executable programs (and actually may still do, in some cases), rather than simply being restricted to configuration files. If memory serves,
ifconfig was actually
/etc/ifconfig on SVR4 systems some years ago.
If you use a Solaris machine, you’ll also see
xpg4 (standing for “X/Open Portability Guide”),
ccs (“C Compiler System”), and
ucb (“University of California, Berkeley” — BSD compatibity).
You may find reading up on the FHS helpful :)