Terminal Services or Terminal Server Edition (TSE) is a component of Microsoft Windows NT operating systems (both client and server versions) that allows a user to access applications or data stored on a remote computer over a network connection. Terminal Services is Microsoft's take on server centric computing, which allows individual users to access network resources easily.
Based on the Remote Desktop Protocol (RDP), Terminal Services was first introduced in Windows NT 4.0 (Terminal Server Edition). The products Windows 2000 Server, Windows 2000 Advanced Server, Windows 2000 Datacenter Server and Windows Server 2003 have introduced several improvements and new features. Microsoft used Terminal Services in Windows XP for the Remote Assistance feature. Windows XP (Professional Edition only) includes a single-user Terminal License using the Remote Desktop feature.
Microsoft provides the client software Remote Desktop Connection (formerly called Terminal Services Client), available for most 32-bit versions of their Windows operating systems and Apple's Mac OS X, that allows a user to connect to a server running Terminal Services. Third-party developers have created client software for other platforms, including the open source rdesktop client for common Unix platforms. Both Terminal Services and Remote Desktop Protocol use Port 3389 by default.
A thin client is a computer (client) in client-server architecture networks which depends primarily on the central server for processing activities. The word "thin" refers to the small boot image which such clients typically require - perhaps no more than required to connect to a network and start up a dedicated web browser or "Remote Desktop" connection such as X11, Citrix ICA, Microsoft RDP or Nomachine NX.
In contrast, a thick or fat client does as much processing as possible and passes only data required for communications and archival storage to the server.