It is a set of Open Source GIS binaries for Windows (win32) and Linux systems.
FWTools is a set of Open Source GIS binaries for Windows (win32) and Linux (x86 32bit) systems produced by Frank Warmerdam (ie.
The FWTools kits also aims to track the latest development versions of the packages included as opposed to official releases. While this may mean the packages are less stable, it is intended to give folks a chance to use the latest and greatest.