That is an 'en passent' capture. Have a Google for full details 👍
Is this a special pawn move?


Yup, "special rule" called "en passant." This chess.com resource shares much more than just the rules; it also shares some useful beginner-strategies: https://www.chess.com/learn-how-to-play-chess This link also has sections hyperlinked near the top and section 3 is titled, "Discover The Special Rules" (which are en passant, castling and promotion).
In that position I would actually capture the hanging e8 bishop, unless there is actually a rook in the a-file which is not shown in the picture.
But not to worry, I had a big shock of my life when I saw that very strange move for the first time.

Fun fact: googling "special pawn move" (as in the title) gives the explanation of en passant immediately. Many other similar expressions also work.
'
3.7.3.1 A pawn occupying a square on the same rank as and on an adjacent file to an opponent’s pawn which has just advanced two squares in one move from its original square may capture this opponent’s pawn as though the latter had been moved only one square.
3.7.3.2 This capture is only legal on the move following this advance and is called an ‘en passant’ capture.'
https://handbook.fide.com/chapter/E012023
Last night I was playing a game with the Chess.com AI. It was "friendly" game so I could ask for hints. The hint I was shown was to move a pawn from f5 to g6, but g6 was empty. That didn't make sense to me. Is there a special pawn move I wasn't aware of or did the AI make a mistake? Thanks.