Comment by tenebrisalietum

The directories that house your executables are read only to users other than root, to prevent attacks and overwriting them by non-root users.

/var stands for variable data--like log files, cache directories, spool directories, etc. You shouldn't put executables there. Ideally you should be able to set the noexec flag on it.

`/usr` actually exists because the original UNIX developers ran out of disk space and had to attach another disk. The difference between /bin and /usr/bin is not worth it and even Debian symlinks /usr/bin to bin.

But your distribution's package manager should be putting stuff in /bin or /usr/bin, not you. Anything that follows the regex "{asterisk}/local{asterisk}" is something the system owner can do whatever with. So you should be using /usr/local/bin or $HOME/local/bin. I don't know why there's no /local off of the root. (One thing I do on my own systems is make and use an /etc/local although I think you're supposed to use something like /usr/local/etc).

/opt is for third party programs that aren't installed via your distro's package manager.

If you do this, any customizations you make to a system can be easily backed up by copying all dirs with local in the name.

There's multiple decades of tradition behind these names, but they do date back to the age where actual teletypes were used.