Below is list of directories and respective details as generally found in /opt/ directory of Mac.
Feel free to comment below if you find new directories (name and details).
/opt/:
- /opt/gtk/
- /opt/gtk/bin/
- /opt/gtk/etc/
- /opt/gtk/lib/
- /opt/gtk/share/
- /opt/vagrant/
- /opt/vagrant/bin/
- /opt/vagrant/embedded/
- /opt/X11/
- /opt/X11/bin/
- /opt/X11/etc/
- /opt/X11/include/
- /opt/X11/lib/
- /opt/X11/libexec/
- /opt/X11/share/
- /opt/X11/var/