Hooks

WordPress hooks are predefined points in the WordPress core code where developers can use them to inject an additional code or modify a variable. WordPress hooks have two types of hooks:

• Actions
• Filters

Action	Filters
Actions allow you to add data or change how WordPress operates. Callback functions for Actions will run at a specific point in the execution of WordPress and can perform some kind of a task, like echoing output to the user or inserting something into the database.	Filters give you the ability to change data during the execution of WordPress. Callback functions for Filters will accept a variable, modify it, and return it. They are meant to work in an isolated manner, and should never have side effects such as affecting global variables and output.
	Filters are used to modify variables. Unlike actions, filters code must return a value, which is the modified copy of the original value.

Example: save_post (Action Hook)

Fires once a post has been saved.

<?php
	add_action("save_post", "callback_method");
	function callback_method( $post_id ){
  		// You can add any code here and it will be executed when the user save s a post.
	}
?>

Example: the_title (Filter Hook)

<?php
	add_filter("the_title" , "capitalize_post_titles" );
	function capitalize_post_titles( $post_title ){
  		
		$title = ucwords(  $post_title  );
   		return $title; 
	}
?>

 

admin_post_action

https://developer.wordpress.org/reference/hooks/admin_post_action/ 

WordPress offers filter hooks to allow plugins to modify various types of internal data at runtime.