What is X-Client?
X-Client refers to the application program running on a X server is displayed even though this application program is otherwise disconnected from this server. Any application program that runs on a GUI provided by the X Window System, virtually any GUI used on Linux and other Unix-like operating systems, is considered an X client. Therefore, Apache, OpenOffice, gFTP, gedit, GIMP, Xpdf and rCalc are typically X clients when used on such operating systems.
An X server is an application program in the X window system that is run on local machines. The X server manages all access to the screens, graphics cards and input devices (e.g. mouse or keyboard) on these computers for the GUIs. The X Window System, also simply called X, is a comprehensive, free client-server system for managing GUIs on individual computers as well as in computer networks.
In the standard client-server architecture, the client program is implemented on the local system and the server program is implemented either on the local system or on the remote system, i.e. on any other system in the Computer network. In the X Window System, however, this architecture is reversed, with each local system implementing the X server program and accessing the X client applications running either on the same system or on a different remote system. Therefore, the application programs do not need to know the specifications of monitors, graphics cards and other installed hardware. This simplifies the creation of such programs and makes it easier for several users in the network to work simultaneously.
One of the main characteristics of the X Window System is its network transparency. This means that practically any X client can run either on the local system or on the remote system without, in most cases, having any obvious influence on the users. This has many important advantages, such as greater ease of use for common users and simplified administration.