PGN is a form of notation that represents a game to a computer the way standard chess notation represents it to a human. you can feed a PGN file to a chess application on your computer and it will then have the whole game available to it so you can open and play the game at any time, keep hitting the "move" button to watch the game be played out, add your own notes for later reference and study, or take the place of one of the players at any point in the game to investigate "what-if" scenarios and such. it's quite a useful feature if you're into all that.

and yes, Abalone is tons of fun. it's actually best when played in person over a physical board because the board's plastic and the marbles are glass and - especially with the first edition which was bigger than the set is now - the aesthetics are very pleasing. the game's beautiful to look at - the hexagonal board with the shiny spherical marbles - and pushing the marbles around feels good and makes a very satisfying "chunk!" sound when they fall into place. but it would be satisfying on here too - just for different reasons.