Terminal Services Gateway vs. Terminal Services RemoteApp: What’s the diff?
Windows Server 2008 offers both Terminal Services Gateway (TS Gateway) and Terminal Services RemoteApp (TS RemoteApp) features. Although they both offer Remote Desktop Protocol (RDP) over HTTPS, the main difference between them is that TS Gateway allows you to publish the entire desktop while TS RemoteApp publishes only the application.
For example, if you have a need to allow one of the vendors access to an application on your network so the vendor can support it you might want to consider TS RemoteApp in Windows Server 2008 as a solution. You can simply publish the application on a Windows Server 2008 in the DMZ, or behind an ISA firewall, without having to worry about setting up Virtual Private Networks (VPNs) for the vendor. As an administrator, you can use the TS Gateway to have full, secure access to the entire desktop.