What happens with Xml Serialization and Private members

[Jax]

Just to confirm.
If I have object foo:

public class foo
{
private string myPrivate;
protected string myProtected;
public string myPublic;

public class foo()
{
myPrivate = "You cant see this!";
myProtected = "Only family can see this";
myPublic = "This is for everyone";
}
}

If that is serialized using xmlserialization only myPublic will be actually serialized in the file.
The next part is what I want to confirm.
When an object is deserialized the type needs to be passed in as well, Is it that becuase serializer needs to read the type to inputs the default value for the private fields when they get back?
Also i'm interested in finding out why XmlSerialization doesn't cover anything private or protected, anyone got any info?

Many thanks
Jax