Whats the difference between a Published RemoteApp and an unpublished RemoteApp?

I'm using Server 2012 R2 and I've noticed the option under "Tasks" to "Publish RemoteApp Program" and "Unpublish RemoteApp Programs".  What are the differences?  

Also how do I allow a published RemoteApp to be accessible to a desktop PC within my network?  Currently everything is accessible through the RD Web Access portal but I would like some apps to be accessible to a workstation on their desktop within my network without having to login into the portal to access the RemoteApp.  I remember there was a way to do this on Server 2008 but I can't remember how.  Suggestions would be appreciated.

Thank you,

Ryan