As we know,Both scope and namespace have to do something with the config/routes.rb file  .Yes,in some way ,both are wrapper for our well-known resources method. First,understand the working of scope by examining how it generates paths.Consider this:

scope 'alpha', module: 'bar', as: 'benz' do
  resources :posts
end

  Prefix Verb   URI Pattern                   Controller#Action
    benz_posts GET    /alpha/posts(.:format)          bar/posts#index
              POST   /alpha/posts(.:format)          bar/posts#create
 new_benz_post GET    /alpha/posts/new(.:format)      bar/posts#new
edit_benz_post GET    /alpha/posts/:id/edit(.:format) bar/posts#edit
     benz_post GET    /alpha/posts/:id(.:format)      bar/posts#show
              PATCH  /alpha/posts/:id(.:format)      bar/posts#update
              PUT    /alpha/posts/:id(.:format)      bar/posts#update
              DELETE /alpha/posts/:id(.:format)      bar/posts#destroy

Now ,Let's analyze the paths being generated by namespace ,if we write something like this :

namespace :alpha do
  resources :posts
end

doing rake routes gives us:

     Prefix Verb   URI Pattern                   Controller#Action
    alpha_posts GET    /alpha/posts(.:format)          alpha/posts#index
              POST   /alpha/posts(.:format)          alpha/posts#create
 new_alpha_post GET    /alpha/posts/new(.:format)      alpha/posts#new
edit_alpha_post GET    /alpha/posts/:id/edit(.:format) alpha/posts#edit
     alpha_post GET    /alpha/posts/:id(.:format)      alpha/posts#show
              PATCH  /alpha/posts/:id(.:format)      alpha/posts#update
              PUT    /alpha/posts/:id(.:format)      alpha/posts#update
              DELETE /alpha/posts/:id(.:format)      alpha/posts#destroy

One thing to note ,When we are working with namespace ,  first create a folder like

app/controllers/alpha and have a structure like this :

module Alpha
  class PostsController < ApplicationController
  
  end
end

Now ,amid all this ,you may ask a very pertinent question "Why do we need them?".

You may wish to organize groups of controllers under a namespace. For example , you might group a number of administrative controllers under an Admin:: namespace .So

namespace is like a wrapper that wraps controllers whom we want to be grouped together.

Thanks for reading.