Fail images are frequent today, huh.
Fate/Stay Night is a revolutionary visual novel from 2006, written by Nasu. It has 3 routes and spawned 2 shitty adaptations. Latter, Gen Urobutchi, with Nasu's supervision, wrote the prequel LN Fate/Zero. In 2011 (Or 2012, don't remember), Ufotable adapted Fate/Zero into a top-notch anime. Now they are adapting 2 routes from the original VN. One as a series, the other as films.
The main plotline of all Fate works focuses on the Holy Grail War. A tournament between 7 "Masters" to win the Holy Grail, which will grant any wish you so desire. To fight in the war, the Masters summons Heroic Spirits, or "Servants", which are legendary people such as King Arthur and Alexander the Great to fight in the war. F/Z focuses on the 4th Grail War, and F/SN focuses on the 5th.
If you want to know more, I recommend watching Fate/Zero, and then either read Fate/Stay Night or wait for the remake. Oh, and the first episode of F/Z is really long and boring, but it gets insanely good after that.