When you run bundle install with a project, it is going to install all the
gems specified by your project in a vendored location relative to the location
of your Ruby version install.
If you want to find the location of a specific gem, you can ask bundler with
bundle show <gem-name>.
Here I ask where the rspec gem is.
$ bundle show rspec
/Users/jbranchaud/.asdf/installs/ruby/3.1.3/lib/ruby/gems/3.1.0/gems/rspec-3.12.0I could cd into that directory to have a look around at the source. That's a
great way to learn more about how our dependencies work.
I could even inject some debugging statements (e.g. binding.irb) which the
program using these gems will break on. Not often, but sometimes you need to
dig in this deep to understand what is causing a tricky bug or why code isn't
behaving like you'd hoped. Just remember to remove those statements when you're
done.