411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. c3/3...f5
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
3...f5
This is the Ponziani Countergambit. It sacrifices the f-pawn, but attacks e4 and prepares to develop the knight on g1. While 4.exf5 is a good move, 4.d4 is probably a better option. If White has studied against this, Black will have a bad time, but if not, both sides will be able to attack in an exciting game.