What does "opt" mean (as in the "opt" directory)? Is it an abbreviation? [closed]
In the old days, "/opt" was used by UNIX vendors like AT&T, Sun, DEC and 3rd-party vendors to hold "Option" packages; i.e. packages that you might have paid extra money for. I don't recall seeing "/opt" on Berkeley BSD UNIX. They used "/usr/local" for stuff that you installed yourself.
But of course, the true "meaning" of the different directories has always been somewhat vague. That is arguably a good thing, because if these directories had precise (and rigidly enforced) meanings you'd end up with a proliferation of different directory names.
According to the Filesystem Hierarchy Standard, /opt is for "the installation of add-on application software packages". /usr/local is "for use by the system administrator when installing software locally".
It's usually describes as for optional add-on software packagessource, or anything that isn't part of the base system. Only some distributions use it, others simply use /usr/local.
OPTional
It holds optional software and packages that you install that are not required for the system to run.