More and more Oracle products are using something called Meta Data Services to store metadata. Metadata is data that describes other pieces of information—where it came from, what it means, or how it is intended to be used. An image captured by a digital camera might include metadata about where and when the picture was taken, which camera settings were used, and so on. In the case of an ADF application, the metadata describes how the application is intended to be used.
There are three kinds of customizations in ADF: