According to "Starting Out: 1.d4!, this is the Gambit of Aleppo, or the Queen's Gambit as modern vulgarians call it, which is indeed the queen of chess openings. Immediately Black choses to accept or decline the gambit. However, according to FCO, Black's principle defenses to this set-up have grown into three major, independent openings: the Queen's Gambit Declined (2...e6), the Slav Defense (2...c6) and the Queen's Gambit Accepted (2...dxc4).