An unfamilar if statement

[eluser]ranjudsokomora[/eluser]
Hello CI Coders,
I think this is an easy one, I just need some pointers. I was looking at modifying the router.php file, and stumbled across this code:

Code:

$this->routes = ( ! isset($route) OR ! is_array($route)) ? array() : $route;

I don't know what the

Code:

? array() : $route

Means, could someone explain or link me documentation on what the question mark, and colon mean?

Thanks