JNLP file extension – Java Network Launching Protocol is used to manage and launch Java applications over web or network, XML (Extensible Markup Language) being its primary element. Moreover, these files are utilized mainly for stand-alone applications; it doesn't run on web browsers of the users. The files get downloaded to the PC, if it is configured properly and runs as a Java program or application.
The file includes href that says about the URL at which the file is stored or located. If you search regarding syntax and more content that is included, it contains specs, application version and codebase. In addition also includes title, shortcuts, menus, permissions for the security and much more.