Impossible move?

No, it is called taking en passant.

When a player has played his pawn up to the 5th or 4th row and the other player moves a pawn of his 2 places PASSING the other pawn. Then the player with a pawn on the 5/4th row can capture like it has only moved one place.
This can only be done by pawns who are next to each other.
And the capture has to be done immediatly after the pawn moved 2 squares, if it isn't captured immediatly you cannot take it en passant in the future.

en-passant (or en-passent), yes it is legal.  A pawn is legally allowed to capture the "jump" square of a pawn that was moved from its starting position if and only if it is done on the opponents (yours) next move.  if its not done immediatly, you lose the ability.  You also might wanna look up Castling if you are new to the game.

The king is allowed to move two spaced to either side, putting the rook to the side of the king (opposite to the rooks starting position), if and only if the king and the rook have not moved yet AND the king is not "passing" through check.  It is possible for a bishop to stop someone from castling

Lastly, it is possible for a pawn to "under-promote" once it reaches the end of the board.  This one i questioned for a while till i looked it up.  For example you dont have to always "queen a pawn" (although there is an option to auto-queen if you play a lot of bullet), you can promote to a rook/bishop/knight as well.

Those are the generally the three noobie questions.  Google fide and look up the official move rules if you dont believe me.  I didnt feel like adding them in myself.  GL out there brosive.

I guess en-passant is left out in "home rules version" where I you play for fun.
I learned chess at the age of 5 years old and played it for fun till I was 30 where I joined a chess club only at that time I learned about en-passant.
I had a chess program that took en-passant before that but I thought it was programming mistake.

thanks for the help