Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...f5/4. Nc3/4...fxe4/5. Nxe4/5...d5/6. Nxe5/6...dxe4/7. Nxc6/7...Qg5/8. Qe2/8...Nf6/9. f4

9...Qxf4 is the main line, because why not take a pawn if White's going to leave them lying around.

9...Qh4+ is similar to the main line, in that the Black queen ends up on h3 via h4 in both lines, except without the bonus of having taken a pawn. A pawn is a pawn!