It is a plugin that allows users to add custom fields to their WordPress posts, pages, and custom post types. It provides an easy-to-use interface for creating custom fields, including text, images, files, and more, without needing to write any code.

Here are the guidelines for using the Advanced Custom Fields plugin:

1. Install and activate the plugin
2. Create custom fields using the visual interface
3. Add custom fields to your posts, pages, or custom post types
4. Display the custom fields in your WordPress theme using shortcodes or PHP functions
5. Manage the display and behavior of custom fields using the plugin settings

People use the Advanced Custom Fields plugin to extend the functionality of their WordPress website and add custom data to their posts and pages. It is a popular plugin for customizing post and page templates, adding custom information to products, and creating custom user profiles.

The Advanced Custom Fields (ACF) plugin and Advanced Custom Fields Pro (ACF) plugin are two different versions of the same plugin with different features and capabilities.

The Advanced Custom Fields (ACF) plugin is a free, basic version of the plugin that provides the core functionality of adding custom fields to WordPress posts, pages, and custom post types.

The Advanced Custom Fields Pro (ACF) plugin, on the other hand, is a paid version of the plugin that offers additional features and capabilities, such as:

1. More field types, including repeater fields, flexible content fields, gallery fields, and more
2. Option to create custom options pages
3. Customization of the WordPress admin interface
4. Advanced form building capabilities
5. Import and export of custom fields
6. Integration with popular page builders
7. Priority support and updates

The Advanced Custom Fields Pro (ACF) plugin is suitable for websites with more advanced custom field requirements and provides a more comprehensive solution for adding custom fields to a WordPress website.