The Packaged Application gallery includes three types of applications: sample applications, productivity applications, and custom applications.
The main difference between a sample and productivity application is the level of support. By default, sample applications are fully editable. In contrast, you must unlock packaged applications before you can edit them. Unlocking an application makes it ineligible for future upgrades or support by Oracle Support.
As the group name implies, an Oracle-supplied sample application is not a complete application but instead contains code snippets or sample code. Sample applications are available for installation in a workspace and are editable by default.
Productivity applications are fully functional applications that have been designed to address a specific business need. You can install, run, and use a productivity application as is, or analyze it to better understand how to build a specific type of functionality. Productivity applications are available for installation in a workspace, but are not be editable by default.
Custom applications are applications you create and that are managed by your instance administrator. Like Oracle-supplied packaged applications, custom packaged applications typically include both the application pages and supporting database objects. A developer creates a custom application using an application export. Once exported, your instance administrator imports it to make it available. Custom applications are available for installation in a workspace, but are not be editable by default.
"Managing Custom Applications" in Oracle Application Express Administration Guide