Chess Opening Theory/1. e4/1...e5/2. Qh5/2...g6
1.e4 e5 2.Qh5 g6
This move is a blunder because this allows 2.Qxe5+! creating a deadly fork to the King and the rook and thus, removes the King's right to castle kingside, and removes his center control. The only good thing about this is that the Queen on h8 is kind of blocked and has no where to go. And when black plays very good plays good moves while white wasn't able to escape his Queen on the side, it could be trapped easily and thus, gaining a major piece which could really help in winning the game.
After 2.Qh5?, g6?? is not really recommended because of the fork on e5. Instead, we should play something like Nf6 attacking the Queen and preventing the famous Scholar's Mate with Bc4. Although this gives white the opportunity to capture on e5, we in return, gains tempo by 3.Qxe5+ Be7 then something like d4 to increase pressure in the center then just Nc6 and attack the Queen. If 4.Qg3?! or 4.Qg5?! attacking the g7 pawn, then simply castle short then we will have a good game.
With black's reaction of Nf6, White has just broke 2 rules in the opening. First, he put his Queen out too early. And second, he has moved a piece more than once before developing the minor pieces. With white having broken already 2 rules in the opening, we can easily have a good game. This is because white has too many Queen moves that he did not have the chance to develop his minor pieces and castle atleast before move 10 while black has developed his minor pieces, has castled already, and gained a tempo. This gives black more chances of winning than white's. In short, black is winning the game.