We'll start off by talking a little bit about the Elixir programming language that Phoenix sits atop. The most important thing to note, especially if you're coming from another programming language such as Ruby, Go, PHP, JavaScript, or Java, is that there is one significant difference between Elixir and the rest: Elixir is a functional language. While this doesn't change everything dramatically, it does introduce a few gotchas that we will need to get out of the way.
If you're already comfortable with Elixir and IEx, feel free to skip this section, as this is intended to be a quick introduction or refresher to the Elixir language and the IEx debugging tool.
Before we dive too far into those gotchas, let's first get acquainted with a tool that is going to make our development process in Elixir much simpler: IEx.