You cannot open or install the game using this file alone. To extract the contents, you need all the other numbered parts (part1, part2, etc.) in the same folder. Once you have the full set, opening "part1" usually triggers the extraction of the entire game.
This filename represents a specific segment of a compressed archive for . Half.Life.2.Episode.One.MULTi18.part3.rar
The title of the game. Released in 2006, this was the first standalone expansion continuing the story of Gordon Freeman after the events of Half-Life 2 . You cannot open or install the game using this file alone