What is Oracle ADF?
On the Internet I found the following definition:
ADF integrates a mix of subframeworks to provide the key functions for object-relational mapping and other forms of service access, data bindings, and user interface, along with the functional glue to hold it all together. ADF stands for 'Applications Development Framework' and it's developed by Oracle. ADF is a framework and it'll help you build your applications easily as many of the redundant things that we do while we develop our applications are taken care by the framework.
But I still have a couple of questions with respect to understanding ADF:
It is a web development framework based on JSF. But heavier!!
If you plan doing web development with this, be warned that this framework is not very flexible. It feels like developing web software as in the 1999 with Visual Studio!!
You build everything in the Oracle IDE JDeveloper (incuding UI!) drag and dropping UI widget already made... If you can live with the default look and feel and do not want to include popular JavaScript libraries (jQUery) you should be fine. For example, building intranet applications could be OK. But if you want to do a public web application (Internet) I would not recommend this framework!