Rails::Railtie is the core of the Rails framework and provides several hooks to extend Rails and/or modify the initialization process.| api.rubyonrails.org
An Engine with the responsibility of coordinating the whole boot process. Initialization Rails::Application is responsible for executing all railties and engines initializers.| api.rubyonrails.org
Railties – Gluing the Engine to the Rails Railties is responsible for gluing all frameworks together.| api.rubyonrails.org
Active Support Message Verifier MessageVerifier makes it easy to generate and verify messages which are signed to prevent tampering. In a Rails application, you can use Rails.application.| api.rubyonrails.org