Laravel AuthServiceProvider code explanation

I'm starting to user Gate in Laravel 5.1, and I got this code from some where in the internet.

<?php    

public function boot(GateContract $gate)
{
    $this->registerPolicies($gate);

    /**
     * NOTE!!
     * First time migration will fails, because permissions table doesn't exists.
     */
    foreach($this->getPermissions() as $permission) {
        $gate->define($permission->path, function($user) use ($permission) {

            return $user->hasRole($permission->roles);
        });
    }
}

My question is, what is function($user) use ($permission) { in $gate->define($permission->path, function($user) use ($permission) { ??? Why is there use after function()?

If there're some references, I'd love to know/ read it.

via Chebli Mohamed