Custodial services involve a third party holding onto your bitcoin on your behalf, which can be convenient but comes with added risk. Self-custody, on the other hand, means you are responsible for keeping your own bitcoin secure, which may require more effort but gives you full control.
If you haven’t read Part 1, you can read it https://www.momentum-analytics.io/news/self-custody-part-1
“There are no shortcuts to any place worth going.” - Beverly Sills