hi there... to whomever it may concern...

maybe i'm just missing something here but i think there's been a glitch in this game i'm playing

http://www.chess.com/echess/game.html?id=8552314

-- the latest move has me quite confused.

could someone help me out and let me know what's going on?

thanks, sorry if this is something simple or something i've just missed.

It is a legal move:

http://en.wikipedia.org/wiki/En_passant

Its an en passant capture.  Perfectly legal chess move.

http://www.chess.com/chessopedia/view/en-passant

It is also a common question.  No need to apologize.

I've never understood why it was added as a rule

It was added as a rule so that you couldn't bypass a capture by moving two squares. And it wasn't just like added recently it's always been there since the beginning of chess.

It hasn't been there since the beginning of chess. It's been there since the rules were changed to allow pawns to move 2 squares on their first turn in an attempt to speed up the game.

Evidently they wanted to speed up the opening without changing the game too much.