The Nix wiki is pretty thorough in most cases however as a newcomer I find it assumes often that the reader has a lot of context / knowledge already.
I wanted to better understand how Nix helps package Ruby application and expand on what was already provided in Packaging/Ruby.
I wrote a small post diving into it that I hope others may find fruitfull
https://fzakaria.com/2020/07/18/what-is-bundlerenv-doing.html