/opt and /usr/local

/usr/local: System software/commands,  for example, the software installed from directly by running installation package.

/opt: Other software (based on my understanding, it can be some open source software). When you have an application installed in /opt directory, you will have:
/opt/<appname>/bin
/opt/<appname>/lib
/opt/<appname>/share/man

conf files in /etc/opt/<appname>/ and logs in /var/opt/<appname>/