1.This is not a standard rails directory, but a directory installed by RSpec in which all test files are kept.
2.The @ indicates that this is an "instance variable". An instance variable defined in the action (or function) of a controller is automatically available in the view of that same name.
3.It's a test that simulates a browser accessing our application.
4. Ruby complains if we try to evaluate an undefined local variable, but issues no such complaint for an instance variable; instead, instance variables are nil if not defined