1. Action Pack: Action Pack is a single gem that contains Action Controller, Action View and Action Dispatch. The “VC” part of “MVC”.

Action Controller: Action Controller is the component that manages the controllers in a Rails application. The Action Controller framework processes incoming requests to a Rails application, extracts parameters, and DISPATCHES them to the intended action.

Services provided by Action Controller include session management, template rendering, and redirect management.

Action View: Action View manages the views of your Rails application. It can create both HTML and XML output by default.

Action View manages rendering templates, including nested and partial templates, and includes built-in AJAX support.

Action Dispatch: Action Dispatch handles routing of web requests and dispatches them as you want, either to your application or any other Rack application. Rack applications are a more advanced topic and are covered in a separate guide called Rails on Rack.

2. Action Mailer: Action Mailer is a framework for building e-mail services. You can use Action Mailer to receive and process incoming email and send simple plain text or complex multipart EMAILS based on flexible templates.
3. Active Model: Active Model provides a defined interface between the Action Pack gem services and Object Relationship Mapping GEMS such as Active Record. Active Model allows Rails to utilize other ORM frameworks in place of Active Record if your application needs this.
4. Active Record: Active Record are LIKE Object Relational Mapping (ORM), where classes are mapped to table, objects are mapped to columns and object attributes are mapped to data in the table.
5. Active Resource: Active Resource provides a framework for managing the connection between business objects and RESTful web services. It implements a way to map web-based resources to local objects with CRUD semantics.
6. Active Support: Active Support is an extensive collection of utility classes and standard Ruby library extensions that are used in Rails, both by the core code and by your applications.

Action Controller: Action Controller is the component that manages the controllers in a Rails application. The Action Controller framework processes incoming requests to a Rails application, extracts parameters, and dispatches them to the intended action.

Services provided by Action Controller include session management, template rendering, and redirect management.

Action View: Action View manages the views of your Rails application. It can create both HTML and XML output by default.

Action View manages rendering templates, including nested and partial templates, and includes built-in AJAX support.

Action Dispatch: Action Dispatch handles routing of web requests and dispatches them as you want, either to your application or any other Rack application. Rack applications are a more advanced topic and are covered in a separate guide called Rails on Rack.