In Ruby what is the meaning of colon after identifier in a Hash?

Question

I\'m learning about Factory Girl and I saw this code:

factory :post do
  association :author, factory: :user, last_name: \"Writely\"
end

why do

Answer 1

Ruby 1.8 syntax:

:factory => :user

Ruby 1.9 syntax:

factory: :user

Note that the Ruby 1.8 syntax works in 1.9 also.