VNC stands for Virtual Network Computing. It is, in essence, a remote display system which allows you to view a computing `desktop' environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures.
It is implemented in a client/server model. This package provides a client for XWindow, with this you can connect to a vncserver somewhere in the network and display its content in a window. There are vncserver available for X and for Win95/NT.
The difference between the xtightvncviewer and the normal vncviewer is the data encoding, optimized for low bandwidth connections. If the client does not support jpeg or zlib encoding it can use the default one. Later versions of xvncviewer (> 3.3.3r2) support a new automatic encoding that should be equally good as the tightvnc encoding.
Other VNC Tools
VNC 'Server side'
conspy - Remote control of Linux virtual consoles
gnome-rdp - remote desktop client for GNOME
krfb - Desktop Sharing for KDE
tightvncserver - virtual network computing server software
vino - VNC server for GNOME
vnc4server - Virtual network computing server software
x11vnc - VNC server to allow remote access to an existing X session
VNC 'Client side'
directvnc - VNC client using the framebuffer as display
gvncviewer - VNC viewer using gtk-vnc
krdc - Remote Desktop Connection for KDE
python-gtk-vnc - A VNC viewer widget for GTK+ (python binding)
ssvnc - Enhanced TightVNC viewer with SSL/SSH tunnel helper
tightvnc-java - TightVNC java applet and command line program
tkvnc - Displays a list of (defined) machines to start VNC to
tsclient - front-end for viewing of remote desktops in GNOME
vinagre - remote desktop client for the GNOME Desktop
vnc-java - VNC java applet and command line program
xrdp - Remote Desktop Protocol (RDP) server
xtightvncviewer - virtual network computing client software for X
xvnc4viewer - Virtual network computing client software for X
pyvnc2swf - screen recording tool to SWF movie
vncsnapshot - A utility that takes JPEG snapshots from VNC servers
x2vnc - A dual-screen hack - link an MS-Windows and X display