Tal Gambit

2...d5 is the Tal gambit.

3. exd5 is the main move. Rather take back immediately, 3...Qxd5, which allows 4. Nc3 to develop with tempo, Black's usual idea is to gambit it: 3...Nf6, threatening d5, allows White the time to defend the pawn with 4. c4?!, but after 4...e6 5. dxe6 Bxe6⩱ Black has a development lead and the initiative and compensation for the pawn.

3. e5 is the usual way to decline the gambit. Though White has a king's side space advantage, this is thought to favour Black, who will be able to develop their queen's bishop before playing ...e6, reaching a "superior" French defence structure.

3. Bb5+, intending to trade off the bishop so White may decline the gambit with ...d3, is solid but largely unexplored.

3. Nf3?! dxe4, a pawn sacrifice line, transposes into the Bastavo gambit otherwise seen in the Dutch variation of Bird's opening (1. f4 d5 2. Nf3 c5 3. e4?! dxe4).

The Tal gambit was pioneered by Latvian grandmaster Mikhail Tal (1936―1992), the eighth world chess champion.

An early appearance of 2...d5 was in Horwitz v Bird, 1851,^[1] which continued 3. exd5 Qxd5. Tal pioneered the continuation 3...Nf6 in Harston v Tal, 1979.^[2]

Wikipedia has related information at Sicilian Defence.

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.