Imagine a paper cup that is lightweight, sturdy, and convenient but able to break down without any toxic residue. Regular trash is not biodegradable, but eco friendly coffee cups can be burned or buried without worry for wildlife. Of course it still looks bad to leave a paper cup lying on the ground, but a paper cup without harmful chemicals is safe to release to the environment.
Paper naturally deteriorates, but it might be protected by a wax coating or otherwise contain chemicals that are inappropriate for animals. A biodegradable cup will hold a hot liquid but also quickly breaks down. Its ingredients are natural and do not poison the environment in any way. It does not choke animals if they dig up the cup and chew on it. It is always best to carry away trash, but safer is better than easier.