Flaw in the site???

Im fairly sleeped deprived at the moment...and i guess i may b seeing things...but analysing my game here...it appears to me that move 16 for black sees my opponent take my pawn by moving sideways and then for some reason moving forwards in one move? i.e my pawn is parallel and yet gets taken. Either im seeing things, or theres a rule im not aware of! Can anyone clear this up?Game 3427852
thanks

en passant

It's explained in the FAQ section of Help.

Thanks. jesus, i cant believe i've never come across that before! Learn something new every day!!