Application extension is related to ClickOnce Package file. You can open application files with Clickonce software.
ClickOnce: It is a sofware that developed for packing various applications and presentation files by Microsoft . This program was developed by Visaul Studio. Applications can only work with .net 2.0 or latter systems. You may need to learn more about Clickonce, in this case check the following link.
What to use application
which page related to application file
application Related Searches
You can check related links about application fileextension.