This doc format works best for me ... just enough to get you started and get results. Digging deeper can be done where required. More like this!
https://seb.jambor.dev/posts/systemd-by-example-part-2-depen...
https://seb.jambor.dev/posts/systemd-by-example-part-3-defin...
https://seb.jambor.dev/posts/systemd-by-example-part-4-insta...