The X-windows system itself is actually a client-server application which is capable of running clients and servers on the same machine, or over a network.
Within the X-windows system, the server software controls the input and output (such as the keyboard, screen display and mouse), while the X-clients are the application programs that need to make use of the server's I/O. The clients and servers communicate via the X communication protocol.
The server software needs to be run on the machine to which the keyboard, display and mouse devices are connected, and will be specific to the particular hardware configuration of the machine.
When you install the X-windows packages you will have the choice at some point of which one of several different X-servers you should install. The choice will be made on the basis of what graphics display card is installed on your machine. Most graphics cards are supported under X-windows in Linux.
Assuming you have a super VGA card of some variety (though the earlier video standards are also supported) then, unless it is also an accelerated or enhanced card of some type, you will probably need to install the server:
XF86_SVGA
The server will be installed in the directory /usr/X11R6/bin and it should be linked to the command X, also in the same directory. In many cases, this will already have been done by the installation script, but, if not, you can perform the link operation manually, with the command:
ln -sf /usr/X11R6/bin/XF86_SVGA /usr/X11R6/bin/X
If at any time you need to change the X-server you are using, then this operation will need to be performed again, but with the new server name inserted in the command line as appropriate.