You use tools like Bundler, RVM, rbenv, or chruby every day. But what are these tools actually doing behind the scenes? Let's take a closer look at how tools like these alter Ruby's behavior by tweaking the environment it runs in. We'll take the mystery out of load paths and gems sets. You'll come away with a better understanding of how tools like RVM work, and a better idea of where to look when they don't do what you expected.