The Queen's Gambit begins 1.d4 d5 2.c4. White offers the c-pawn to lure Black's d-pawn away from the centre. It is not a real gambit: if Black takes with 2...dxc4, White regains the pawn in most lines with e3 and Bxc4, or with an early Qa4+.
Black's main replies are 2...e6, the Queen's Gambit Declined; 2...c6, the Slav Defense; and 2...dxc4, the Queen's Gambit Accepted. Each leads to a different kind of game, but in all of them the fight is about the d5 square and the c- and e-pawn breaks.
The 2020 Netflix series of the same name made the opening famous outside chess, but it has been a mainstay of top-level play for more than a century.