Advanced Custom Fields (ACF) is a plugin for WordPress that enables developers to add custom fields to their posts and pages. ACF is particularly useful for adding data that is specific to a particular post or page, such as geo-location data, metadata, or customer information. In addition to being able to add custom fields to posts and pages, ACF also provides a number of other features, including the ability to create custom field groups, which can be used to organize sets of related fields. ACF is an essential tool for any WordPress developer who needs to store and display data that is not part of the standard WordPress content model.