When you start an IEx session, you do so in the context of some directory -- the current working directory. This context can be important if you need to do something like import a file. In fact, you may want to know what files are available in the current working directory.
You can list them all out within IEx using
iex(1)> ls() .git .gitignore README.md _build assets config deps lib mix.exs mix.lock priv test tmp
You can also list the contents of some other specific directory by naming it
h() within IEx for more details.