What is a closure in PHP and why is the use operator needed?

Hello everyone! I started learning PHP and came across the topic of anonymous functions and closures. I think I figured out anonymous functions, but when I got to closures, I stumbled on the `use` operator. Here's the code I saw in the documentation: ```php $message = "Hello, world!"; $greeting = function() use ($message) { echo $message; }; $greeting(); ``` I understand that this works, but I don't understand why this `use` is needed. Why can't I just access the `$message` variable inside the function, like in regular functions? For example: ```php function test() { echo $message; // Why doesn't this work? } ``` I also read that closures can "capture" variables from the outer scope. What does that mean? And why use closures at all if you can just pass a variable