Thank you, everyone. Blueemi I see this game on Internet as a defense. Quite complicated but it's clear. However, I have a doubt. On the Internet, a classical Damiano defense is: e4, e5, Nf3, f6 ... and then not necessarily the d6 of my opponent like in this game:
https://www.chess.com/game/live/30494370735
Considering this small difference we can still talk about Damiano's defense? I ask this just to understand if I really need to focus on Damiano's defense to neutralize this recurring defense I noticed during my game.
White will normally answer 1. e4 e5 2. Nf3 f6 with 3. Nxe5 as given in my post above.
1) Is it correct in Chess says that White always do an "Opening" and a Black always a "defense"?
+ Yes, White plays Ruy Lopez Opening, Italian Opening, Black plays Sicilian Defence, French Defence, Nimzovich Indidian Defence, King's Indian Defence etc. It is just a convention.
2) What is the name of this defense?
For the names: first is Damiano Defence, second is Philidor, third is French/Caro-Kann Hybrid. The names do not matter. The moves are no good.
3) How to react to this defense?
1st game 1 e4 e5 2 Nf3 f6? 3 Nxe5!
2nd game 1 e4 e5 2 Nf3 d6 3 d4 f6? 4 Bc4 and all white squares on the black camp are weak
3rd game 1 e4 e6 2 d4 d5 3 Nc3 c6? 4 Bd3 with a big lead in development
4) What is the difference when this triangle has the vertex in front of the King and in front of the Queen?
c6-d5-e6 is not as weak as d6-e5-f6
c6 blocks the natural move Nc6, e6 blocks the diagonal of Bc8
d6 blocks the natural move Nf6, d6 blocks the diagonal of Bf8, f6 also weakens the white squares e6 and g6; the black king is unsafe
#1 is Wrong! Not everything White plays is an "Opening". In fact, the name is driven by which side makes the final deciding move of what opening it is whether it is an Opening, Defense, SYSTEM, ATTACK, GAMBIT, etc.
So NO! Not everything White plays is an opening and everything Black plays is a defense. Simply WRONG!
Case in point!
A) 1.e4 (This does not define any opening or attack) e6 (This defines the Opening and is hence a DEFENSE, namely the FRENCH DEFENSE
B) 1.d4 (Undefined) Nf6 (Still undefined) 2.Nf3 (still undefined) e6 (Still undefined) and now:
3.Bg5 is the Torre ATTACK
3.Bf4 is the London SYSTEM
3.e3 is the Colle SYSTEM
C) 1.e4 (undefined) e5 (undefined) 2.Nf3 (undefined) Nc6 (undefined - 2...Nf6 would be the Russian DEFENSE) 3.Bb5 is the Spanish OPENING
D) 1.e4 e5 2.f4 is the King's GAMBIT
E) 1.e4 e5 2.Nf3 f5 is the Latvian GAMBIT!
So notice that the name is defined by who makes the DEFINING move of the opening.
If it is defined by White's move, It can be an Opening, Attack, System, Gambit, or have no suffix (the Catalan is simply, "The Catalan")
If it is defined by Black's move, it can be a Defense or a Gambit.
As far as #4 is concerned, How strong or weak c6-d5-e6 is depends on what White has played.
1.d4 d5 2.c4 e6 3.Nc3 c6 is actually known as The Triangle. It is an offshoot of the Semi-Slav with the flexibility of still playing the Stonewall Dutch if 4.e3 (Black can also still play the Semi-Slav with 4...Nf6), and the Noteboom (4...dxc4) against 4.Nc3.
Outside of this, all of those Triangle responses are Garbage except the Fantasy Variation of the Caro-Kann (1.e4 c6 2.d4 d5 3.f3 e6).
Case in point:
1.e4 e6 2.d4 d5 3.e5 c6 - Why? Your d5-point is secure given White's advance of e5. 3...c6 is an utter waste of time. Black should hit White's center immediately with 3...c5 or look to trade Bishops with 3...b6. 3...c6 is just idiotic and Bad for Black.
1.e4 e5 2.Nf3 d6 3.d4 f6 - As mentioned, this severely weakens the light squares, but it also serves no purpose as it simply takes over the square that the Knight belongs on.
The thing the OP needs to do is stop looking at the shape that the pieces make, and instead look for squares that are in White's control, squares that are in Black's control, and weaknesses.
Example: 1.e4 e6 2.d4 d5 3.Nc3 Nf6 4.Bg5 Be7 5.e5 Nfd7 6.Bxe7 Qxe7 7.f4 O-O 8.Nf3 c5.
The e5 square is completely in WHITE'S control right now.
The e4 square, while not occupied, is completely in BLACK'S control right now.
Black can attack e5 with ...f6 while White can attack e4 with f3. Therefore, while these squares are each controlled currently by one side, they are not weaknesses.
However, with Black having pushed e6, d5, and c5, and the dark squared Bishops traded off, the d6-Square for Black is a WEAKNESS. Black must use other means to fight this square, like play ...a6 and maintain the pawn on d5 to not let a knight in. If a Knight does get in, undermine e5 (Attack what protects the knight on d6.)
What the OP needs is a book on Strategy, not Openings.