How opening moves determine the whole game play? I started chess some time ago. I was studying opening theory and it seems most opening moves characterize the style of play.
I want to ask how can a couple of moves determine the whole game play? For example, the french defense is known to be solid and offers counter-attacking chances. How can two moves i.e. e4 e6 d4 d5 say so much about the game?

With my limited experience, I can only think of the following reason:-
1) Pawn structure: Since pawns cannot be moved backwards, so depending on your first moves, the best moves that you can play usually depend on your opening.

Any more reasons? If possible, please explain in general and also the particular case of french defense. Thanks.
Your intuition is right; it's all about the pawns.


As you note, they can't move backwards.
They can't capture straight ahead, so two opposing pawns facing each other (say on e4 and e5) can't move.
They are the least valuable piece, so no one (generally) will capture one with a piece if their piece can be recaptured in turn. So (generally) the only thing that gets exchanged for a pawn is another pawn, which can be hard to make happen because of the way they move.


As a result of all of this, your pawn structure is (generally) the least dynamic part of your position, and all your other piece movement is in relation to it. These pawn structures are often set pretty early in the opening, so they recur a lot and people have studied them very deeply.