What is the difference between t.belongs_to and t.references in rails?

What is the difference between t.references and t.belongs_to? Why are we having those two different words? It seems to me they do the same thing? Tried some Google search, but find no explanation.

class CreateFoos < ActiveRecord::Migration
  def change
    create_table :foos do |t|
      t.references :bar
      t开发者_如何转开发.belongs_to :baz
      # The two above seems to give similar results
      t.belongs_to :fooable, :polymorphic => true
      # I have not tried polymorphic with t.references
      t.timestamps
    end
  end
end

Looking at the source code, they do the same exact thing -- belongs_to is an alias of reference:

  def references(*args)
    options = args.extract_options!
    polymorphic = options.delete(:polymorphic)
    args.each do |col|
      column("#{col}_id", :integer, options)
      column("#{col}_type", :string, polymorphic.is_a?(Hash) ? polymorphic : options) unless polymorphic.nil?
    end
  end
  alias :belongs_to :references

This is just a way of making your code more readable -- it's nice to be able to put belongs_to in your migrations when appropriate, and stick to references for other sorts of associations.