Global data type differs from Page data folder type in mechanism of creating data items and existence of page references.

Data items can be added to Page Data folder type only if data folder has been added to a page. Each data item of page data folder type contains a reference to a page that it has been added to.

Global data type is different because it has no reference to a page, and data items can be added right after data type creation.

How to define when to use Global data type and when Page data folder type?

If you need data shared between many pages, the best choice is Global data type.

You can use C1 functions to render its items on the pages.

Each data type has a predefined C1 function Get<datatypename>Xml, this function can be called in an XSLT function and the XSLT function, in turn, will render it. The XSLT function can be inserted in on a page in the Content perspective.

If you have data that is specific to one particular page, then you should use Page data folder type and add it to this particular page only .

For example, you have a page called "Contacts" and page data folder type that contains addresses of all offices around the world.

It makes no sense to add this data type to the Home page or other ones, because this data is pertaining only to this page.

You can create a Visual function, or a function of some other type, that renders it and insert the function on the "Contacts" page.