/opt 目录一般用于存放第三方的可选的（Optional）软件包，一些系统中的 /usr/local 亦有类似的作用。

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.

https://stackoverflow.com/a/12649407/2609042