What Is This Explaining?

What Is This Explaining?

Working through Rails Tutorial; I'm in the Rails Console mode, or rather,
Development Mode, by running 'rails console'. I'm following Hartl's great
tutorial, and I'm presented with:
NoMethodError: undefined method `empty?' for nil:NilClass
from (irb):7
from
/Users/coreymkimball/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in
`start'
from
/Users/coreymkimball/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in
`start'
from
/Users/coreymkimball/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/railties-4.0.0/lib/rails/commands.rb:64:in
`<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
when I run: 'nil.empty?'
and in Hartl's tutorial it shows this as being presented after running the
command:
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.empty?
My question is, what is all the additional details with my directory, and
the different folders (what it looks like)?
Learning Rails, thanks for the tips.