In this game, all rules of the normal chess game apply, but queens additionally may also move as knights. Queens with such a power are called amazons, hence the name of this game.
This simple rule change makes the queens much more powerful. It has a long history; in some parts of Europe at the end of the middle ages, this was the used rule in the chess game, as was usual at that time in those parts. However, the usual rule of queen movement won `the battle'; probably because with the amazon move, the queen becomes too powerful.
A similar, more recent game with changed queens move is Almost chess.