The Extension Properties

Command

The path of the program associated with the extension. You can change the program by using the [ Browse... ] button to select another one from the project.

MIME type

Defines the content type of the files with the selected extension. This content type will be used by the browsers to select an application to handle a downloaded file. Leave this field empty if you do not want to register a MIME type for the files with the current extension.

Consult the IANA registry online for a list of assigned MIME Media Types.