Region is a part of an Oracle Apps Framework page which acts as a container for the items or components. By default the top most level of an OA Framework page has to be of the “pageLayout” region type.
In OA Framework or OAF the regions can be nested so as to provide the desired layout to the OAF page. Each region is a java bean which acts as a container for the sub-regions or items in any Oracle Application Framework page.
Regions which are parallel in the bean hierarchy, in an OAF page, are called as Siblings and the regions inside a region in an OAF page are called Child regions. The same nomenclature is also applied for Items in OAF. Hence, by default all the regions that you create become the child regions of the pageLayout region as mentioned earlier that the pageLayout region is the top most region in any OA Framework page.
Also every region in OAF has specific properties which can be given some values while creation of the OA Framework page e.g. rendered property which allows the region to be displayed onto the OAF page, as per Oracle Application Framework guidelines (called as OAF standards) this rendered property can have 2 values namely true(visible) or false(hidden). If the region in an OAF page is set to be hidden then all the children regions/items will by default be rendered false once that OAF page is rendered on to screen. Even these properties can be changed at run-time using a Java controller, but that needs an understanding on how to import the region beans and then how to create handle of the bean and then how to set properties. However this is not so much difficult to do but still some Java concept and Java programming knowledge is needed to achieve this. This is called as run-time control of the bean in OAF and is explained in detail for every region in the corresponding region type.
Every region has a specific way of representing the data onto the screen once the OA Framework page is rendered. Hence while creation of a OAF page we have to very cautious in choosing the type of regions. E.g. a defaultDoubleColumn type of region will create two columns and will automatically render all the components created inside it in these two columns once the OAF page is rendered to screen. There are various types of regions available in OA Framework.