Portal applications are packaged in PAR (Portal Archive) files. A PAR file is a standard ZIP file with a .par extension that contains a deployment descriptor, all Java classes, Web resources and other files required to run the application.
Within the portal, the name of the PAR file is the name of the application. The fully qualified name of any component or service defined in the PAR is the name of the PAR file, followed by a period (.) and then the name of the component or service.
A PAR file contains the following files which are divided into two types:
All files in a PAR file that are accessible directly via an HTTP request, such as:
○ Stylesheets (.css)
Web resource files can be located anywhere outside the top-level PORTAL-INF and META-INF folders.
You can create links to these files directly.
Java Classes and Deployment Descriptor
Java classes that implement the component and services defined in the PAR file, plus the deployment descriptor (portalapp.xml). The deployment descriptor specifies the components and services contained in the PAR file, and defines the configuration for the application, components and services.
Read the below link for the additional information