Classes (category)

Walker{}

Class for displaying various tree-like structures. Used as a basis for creating your own subclass.
Walker_Nav_Menu{}

The core class of WordPress that generates the HTML code for the navigation menu items list of WordPress.
WP_Admin_Bar{}

WordPress class for creating the admin bar, which is located at the top of each page when you are logged in.
WP_Comment_Query{}

Selects comments from the database based on the passed parameters. Based on this class, the function get_comments() works.
WP_Date_Query{}

Class for creating the WHERE part of an SQL query. Creates a part of the query related to date selection.
WP_Error{}

A class whose task is to simplify error (message) handling when working with WordPress (creating plugins, themes). This class is used for error handling by WordPress itself.
WP_HTML_Processor{}

Class used for parsing and modifying an HTML document.
WP_List_Table{}

Basic class for creating tables with a list of anything in WordPress. The tables support AJAX technology. All types of tables in the WordPress admin panel are based on this class.
WP_List_Util{}

Service class with utility methods for working with arrays and objects. Helps to sort and filter arrays.
WP_Meta_Query{}

The class creates JOIN and WHERE parts of the SQL query, which, in addition to the main query, will filter the result by the specified key and value of the meta-field.
WP_Post_Type{}

Class of the core that is responsible for all types of WordPress posts.
WP_Query{}

The WordPress Query class. Selects posts from the database based on the specified parameters. get_posts(), query_posts() and all other query functions for posts selection from wp_posts table are based on this class.
WP_Rewrite{}

Class of the core that parses the requested URL (SEO-friendly) and creates a "internal" URL understandable for WordPress. This class is used as an API for creating SEO-friendly links.
WP_Sitemaps_Provider{}

Basic abstract class for creating a Sitemap provider in WordPress.
WP_Term{}

Class of the core, which is used to obtain a taxonomy element or to convert the provided term data into a standard object.
WP_Term_Query{}

Class used for creating queries for taxonomy elements (terms).
WP_User{}

WordPress class that works with a single user: allows you to get user data, remove/add capabilities, etc.
WP_Widget_Archives{}

Class of the core for implementing the "Archives" widget.
wpdb{}

Allows performing any operations with the WordPress database: inserting, updating, retrieving, or deleting data.