Nightmare_Moon.zip is a release file of the Minecraft map Nightmare Moon: Introducing PTK, made for Minecraft 1.7.4. It was published on February 10, 2014 and is 4.7 MB in size. For the full description, screenshots and every other version, visit the Nightmare Moon: Introducing PTK map page.
How to install: Extract the .zip and move the world folder into .minecraft/saves; the map then appears in your Singleplayer list.