"Pack 1090.rar" typically refers to a compressed archive containing a collection of assets. Depending on where you found it, it likely falls into one of these categories:
Image files often used for textures or icons. .md2 / .obj: 3D models. pack 1090.rar
Configuration files that tell a program how to use the pack. Computer Gaming World Issue 175 "Pack 1090
Used for older titles like Quake II or Kingpin: Life of Crime , where community-made texture packs or "gang" packs are common. pack 1090.rar