There is only one file type that uses the .PBN extension:
Portable Bridge Notation File
Game file created in the Portable Bridge Notation (PBN) format, a standard format used for storing data for the card game Bridge; can save the results of a game as well as specify rules for dealing, bidding, playing, and teaching; allows data from one bridge game to be used in another game.
The PBN format is based on the Portable Game Notation (PGN) format, which is used for chess games.
Updated: August 27, 2011