_1.5__R3D_CRAFT_Default_Realism_128x128__75__.zip is a release file of the Minecraft resource pack R3D CRAFT: Default Realism 128px, made for Minecraft 1.5.1. It was published on March 27, 2013 and is 23 MB in size. For the full description, screenshots and every other version, visit the R3D CRAFT: Default Realism 128px resource pack page.
How to install: Put the .zip into .minecraft/resourcepacks (do not extract it) and enable it under Options → Resource Packs.