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
Notifications ActiveSupport::Notifications provides an instrumentation API for Ruby. Instrumenters To instrument an event you just need to do: ActiveSupport::Notifications.| api.rubyonrails.org