To start a game with a specific opening, go to online chess, select start a new game, and then show advanced options. You can then set the starting position to whatever you want.

PGN is Portable Game Notation: it's a format for storing the moves and other details of a game in a text file.

 Post Game Neurosis?        I give up Peter   what does it mean?   !                       Brian...from Danvers MA  

PGN stands for Portable Game Notation. It's a computer format for recording chess games. Basically pgn-files are just text files where the moves are recorded using algebraic notation so you can even open them using Notepad or any other text editor but most chess software also supports pgn.