User applications are programs that you interact with in order to work with the process or process data. User applications also create and use configuration files.
The Alarm Summary Object (OCX) is an example of a user application. It requires you to interact with the system by manipulating the Alarm Summary Object that is embedded in your picture.
Some programs may serve as more than one kind of application. For example, the Database Manager is a user configuration application for creating process databases. However, Database Manager also acts as a user application because it allows you to display real-time data in spreadsheet form.