Before going for details.

Question 1:-- Whats the meaning of scope here (ie named scope)? whats the benefits of using named scope?

Now:-

from agile development with rails book:--

class Order < ActiveRecord::Base
   named_scope :last_n_days, lambda { |days| {:conditions =>
  ['updated < ?' , days] } }

 named_scope :checks, :conditions => {:pay_type => :check}
end

Such a named scope would make finding the last weeks worth of orders a snap.

   orders = Orders.last_n_days(7)

Scopes can also be combined

orders = Orders.checks.last_n_days(7)

why we are using named_scope here. We can do the same using methods. Whats special thing we got using named_scope.