Fate/zero is the novel prequel to Type-Moon’s popular Fate/stay Night. As the first story in the Fate series, it essentially kicks off the Holy Grail War storyline, telling the adventures of Emiya Shirou’s father, who was also Master to Saber in the fourth war ten years prior to Fate/stay Night.
Fate/zero is getting an anime series, although details on this front are scarce. We do know that, following their work on Kara no Kyoukai, Type-Moon have handed the anime reins over to Ufotable, who will be adapting the series into animated form.
Fate/stay Night already has two animated adaptations based on it so far, both by Studio Deen. The first is the original 2006 anime series that covers the “Fate” scenario, and the second is the more recent Unlimited Blade Works movie.