Car makes rattling noise when it starts, but drives fine?

So i went to start my car this morning, when i did there was a loud rattling noise in my car. the car drives perfectly fine, when in reverse or drive it works fine, but the noise is still there, just not as loud as it is when the cars in neutral. i dont have much knowledge about cars or car engines, but i think it might have something to do with the starter or engine? much help is appreciated if anyone knows the problem, thank you!