XSD - Difference between element ref and element type

Hi experts,

   Could someone here please explain me the difference between these two
ways of defining elements,

<xsd:element name="aggregateElement" type="base:baseType"/>

<xsd:element ref="base:baseElement"/>

The only difference that I could understand is the one specified in this
article [1], which says that during an import, 
elements created with ref retains the Namespace of the schema from which
it is imported.

That seams to be an obvious difference. I am not clear on when to use
*type=* style and when to use *ref=* style.

Thanks in advance for any help,

Regards,

Unni.

[1] -
http://developers.sun.com/jsenterprise/nb_enterprise_pack/reference/tech
art/namespaces2.html