Italian Gambit

The Italian Gambit is a chess opening that begins with the moves:

1. e4 e5

2. Nf3 Nc6

3. Bc4 Bc5

4. d4

It is often played as an alternative to the quiet and closed lines of the Giuoco Piano or Giuoco Pianissimo openings. Black can:

take with the pawn (4...exd4), a transposition to the Scotch Gambit;
take with the knight (4...Nxd4), which is considered weak since it allows 5.Nxe5, attacking f7 with the bishop and knight; or
take with the bishop (4...Bxd4), which is considered best.

This article uses algebraic notation to describe chess moves.

4...Bxd4

After 4...Bxd4 5.Nxd4 Nxd4:

6.0-0, favoured by George Koltanowski, transposes to the related gambit line 4.0-0 Nf6 5.d4 following 6...Nf6, when 7.f4 and 7.Bg5 are the main possibilities for White; however, 6...d6!? is an independent alternative for Black.
6.Be3, dubbed the Miami Variation by Jude Acers and George Laven, is a way for White to deviate that probably suffices for dynamic equality.
6.f4?! is considered dubious due to 6...d6.

The Wikibook Chess Opening Theory has a page on the topic of: Italian Gambit

Hooper, David and Kenneth Whyld (1996). The Oxford Companion to Chess. Oxford University. ISBN 0-19-280049-3.
Acers, Jude; Laven, George (2003). The Italian Gambit (and) A Guiding Repertoire for White–1.e4!. Trafford Publishing. ISBN 1-55369-604-2.^{[self-published source]}