A QVD is one logical QlikView table stored on disk in an effcient manner which can be consumed by one or more load scripts since different applications might have a need to use the same data. It is helpful as intermediary staging which also could include keeping history and supporting incremental/delta load scenarios.
QVDs can be created by a load script with the help of a STORE statement:
STORE [CustomersTable] INTO [Customers.QVD] (QVD);
They can also be stored interactively by the users/designers/developers of a QlikView application by using export options built into the UI.
And from the internal Module/Macro VBScript/JScript by writing macro code using QlikVjews object model.
Or via your own program controlling QlikView via Windows Automation using the same QlikView object model that the internal macro use.
There are also some third party utilities and orograms that can produce QVDs without the help of QlikView.
