A unanimous definition of  a scope in rails can be termed as a succinct way of creating database queries. We define a scope in a Model class in the purview of MVC architecture.

It's syntax goes like: scope(name, body, &block) .

To give a basic feeling of what does a scope do ,consider the following example.But remember we use scopes for much complex functionalities.

class Blog < ActiveRecord::Base
  scope :current_status, -> status { where(status: status) }
  scope :latest, -> { order("blogs.created_at ASC") }
end

here ,we have two scopes named current_status and latest ,the first one simply assigns a status for a particular blog and the second scope namely latest sorts the entire blogs in the ascending order of their creation time.

Blog.current_status('pending').recent
# SELECT "blogs".* FROM "blogs" WHERE "blogs"."status" = 'pending' 
#   ORDER BY blogs.created_at ASC

The same task can be achieved using class-methods instead of using scopes :

class Blog < ActiveRecord::Base
  def self.current_status(status)
    where(status: status)
  end
  
  def self.latest
    order("blogs.created_at ASC")
  end
end

A call to a scope returns an ActiveRecord::Relation object that allows for further chaining with other scopes.

Thanks.