see Chess openings
This is Black's most dynamic response to the infrequently played Bird's Opening, immediately challenging for control of the center and offering a gambit pawn in return for quick development. Black hopes to expose the weaknesses of White's first move (1.f4) which weakens the pawn cover around his king. The first few moves are typically as follows:
As can be seen, the game has taken on a tactical and complicated character quite quickly, which may not be what a player of Bird's Opening desires, as it tends to be an opening suited to slower, more strategic players. White has to be careful in the first few moves - for example, if instead of 4.Nf3 he plays his other knight out, he will get checkmated:
5.g3 Qxg3+! (taking with the queen for extra style!)
Of course, as we all know, this kind of thing would never happen in a real game.
White's best response to the From Gambit is probably to transpose into a King's Gambit by playing:
Though the King's Gambit may not be to everyone's taste, it gives much better prospects for White than the main lines of the From Gambit, especially for players who enjoy to take the initiative from an early stage. In fact, this is the main reason why some Black players will not respond to Bird's Opening with the From Gambit.