What is functions.php in WordPress?

Functions.php is one of the theme files that is being wordpress.Every theme has almost their own functions.php file where we can add our custom functions and use the different hooks and filters in wordpress

Functions.php gives us flexibility to write our custom code and link to a hook instead of writing a plugin write from the scratch

For example: If we want to auto login a user we can just add our function and link it to the hook called “auto_login”