Diference between 'private function' and 'private static function'?

Something that’s been bugging me - is there a difference between classifying a function ‘private’ or ‘private static’ in a singleton? It seems that they both do the same thing. Maybe some difference in performance?


package {
    public final class MyStaticClass {
        public function MyStaticClass():void {
            throw Error('Static class!');
        }
        private static function doSomething():void {      
        }
        private function doSomething():void {      
        }
    }
}