Z: What the difference between shy and quiet?

I used to think that shyness and quietness were the same thing, I thought that some people were loud（like me), and that others weres quiet because they had shy personalities, but after teaching in china for a few years, I have come to realize that there is in fact quiet a difference between being shy and being quiet, all shy people are probably quiet,but not all quiet people are shy!
I believe quiet peolpe can learn english very well while shy people will almost always struggle.
In my opinon, quiet people know when they should speak and when they should be quiet, yet, they are always listening and learning from others, generally, they like to listen to what others say before they give their opinion, and when they do say something, their words are well thought out.

Quiet people will usually not be the first to answen a question or make a comments in class. They often wait for teacher to call on them, But if they are called upon, they will usually give a very intelligent and coherent answer.
Shy people, on the other hand, are inflicted with some emotional or mental blockade that creates fear in their minds every time they have to talk in front of others. Perhaps they have self confidence issues or maybe they grew up in an environment were they were too often alone. Whatever the reasons, shy people will too often freeze up when they have to speak to others or in front of others.
For them, perhaps, even listening to others is a bit scary because they are always afraid that they might be called on next!
I am not a psychologist and what I have written above is just my opinion. But I do feel sorry for the shy people in my classes because I am afraid that they will not get the most out of their major. They will struggle and perhaps even fail.
So how we can help shy people? Is there a cure for shyness? Is there therapy? Were any of you shy at one time but you managed to pull yourself out of it?
Comments welcome below.