It's not really obsure but maybe not so easy to explain. Assume you are white and have a pawn on e5 and black now plays d5. The idea of a pawn moving two spaces on its first move is NOT meant to help it evade capture by an enemy pawn...white may now make the capture of blacks d-pawn AS IF it had only moved to d6!.
This 'en passant' rule is only available immediately after black played d5. En passant means "in passing"...white captured on d6 as if he attacked the black pawn as it was passing through the square d6 (hoping to make it to d5 without attack from the white pawn) If you don't know the algebraic designations ("e5"😉 then look them up and this should be clear
um
en passant= taking an enemy pawn with your pawn by moving behing them
requirements...
1. your pawn must be on the same rank as the enemy pawn and next to it, rank 5 if your white and 4 if your black.
2. can only be used the turn right after the pawn power, two square movement by the enemy pawn, is used.
3.isolatedpawn is the best player in rhc