A hook allows one piece of code to interact with or change another piece of code at predetermined, particular locations. In addition to being widely used by WordPress Core itself, they provide as the basis for how plugins and themes communicate with it.
There are two types of hooks:
You can add information or modify WordPress’s functionality with actions. Plugins, themes, and WordPress Core will all execute actions at a given moment. Tasks such as entering data into the database or relaying output to the user can be carried out by callback functions for Actions. The calling Action hook does not get any output from callback routines for an Action.
Filters allow you to modify data while WordPress Core, plugins, and themes are running. Filter callback functions take a variable, change it, and then return the modified value. They should never have side effects like altering output and global variables because they are designed to function independently. Filters anticipate being given something back.
Both require writing a custom function called a Callback and registering it with a WordPress hook for a certain action or filter.
Although WordPress offers a variety of hooks, you may also make your own to allow other developers to expand and alter your theme or plugin.
Actions vs. Filters
Difference between Actions & Filters:
- An action uses the information it receives, performs an action, and then returns nothing. To put it another way, it does something and then leaves without giving the caller hook anything back.
- A filter returns the information after making certain changes to it. To put it another way, it filters something before returning it to the hook for additional usage.