Explanation/Reference:
A high-trust app for SharePoint is primarily intended for use in an on-premises environment. The high-trust app cannot be installed to Microsoft SharePoint Online, and the remote components are typically installed on premises, too, within the corporate firewall. Thus, the instances of the app for SharePoint are specific to each individual company.
High-trust apps require some configuration on the SharePoint farm and on the server hosting the remote web application.
Reference: Create high-trust apps for SharePoint 2013
https://msdn.microsoft.com/en-us/library/office/fp179901.aspx