An Oracle APEX application is an HTML interface that exists on top of database objects such as tables or procedures.
An application is a collection of pages linked together using navigation menus, tabs, buttons, or hypertext links. Application pages share a common session state and authentication.
To create an application, a developer runs the Create Application Wizard to declaratively assemble pages and navigation. Individual pages are organized using containers called regions. Regions can contain text, custom PL/SQL, reports, charts, maps, calendars, web service content, or forms. Forms are made up of fields (called items) which can be selected from the multitude of built-in types (such as text fields, text areas, radio groups, select lists, checkboxes, date pickers, and popup list of values).
Developers can also create their own custom item types using plug-ins. Session state (or application context) is transparently managed and the user interface presentation is separated from the application logic enabling developers to manage the look and feel of an application by simply selecting a different theme.
What Is an Application Page?
A page is the basic building block of an application. Every application consists of one or multiple pages. Each page can have buttons and fields (called items) which are grouped into containers called regions. Pages can include application logic (or processes). You can branch from one page to the next using conditional navigation; perform calculations (called computations); perform validations (such as edit checks); and display reports, calendars, and charts. You view and edit a page in Page Designer.