Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Bxc6/4...dxc6/5. O-O/5...Bg4/6. h3/6...h5

Ruy Lopez, Exchange Variation, Alapin Gambit
After h5, black sacrifices the bishop for the betterment of Black's position. 7. hxg4? is bad because after 7. ...hxg4! the knight on f3 is attacked, and moving the knight is even worse. For example, after 8. Nxe5??, white captures the pawn, but after 8. ...Qh4! the checkmate in four moves is unavoidable. White can also try 7. c3 with the idea of playing d4, but 7. ...Qd3 stops it. 8. hxg4, hxg4. 9. Nxe5, there is a move Bd6, attacking the knight. 10. Nxd3 and then, there is 10. ...Bh2+ and you repeat moves. And white can also play 7. d4 with the idea of developing queenside pieces.

Theory Table
For explanation of theory tables, see theory table and for notation, see algebraic notation..

'''1. e4, e5. 2. Nf3, Nc6. 3. Bb5, a6. 4. Bxc6, dxc6. 5. O-O, Bg4. 6. h3, h5'''