What's the difference between -Dconfig.resource and -Dconfig.file in akka?

System properties can be used to force a different configuration source:

• config.resource
  
  specifies a resource name - not a base name, i.e. application.conf is not an application
• config.file
  
  specifies the path to the filesystem, it must include the extension, not the base name
• config.url
  
  indicates url

Loading configuration with -Dconfig.file

is a way to specify an external file to load,

-Dconfig.resource

- for internal resources.

Taken from: Configuration File Syntax and Functions .