The Elephant Trap
The d5 pawn looks loose because the knight on f6 is pinned, but the pin is not real.
Opening: Queen's Gambit Declined. Set by Black. Level: Intermediate.
Practise setting and escaping itThe moves
1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Bg5 Nbd7 5.cxd5 exd5 6.Nxd5 Nxd5 7.Bxd8 Bb4+ 8.Qd2 Bxd2+ 9.Kxd2 Kxd8
It only works after a mistake
White must play Nxd5 for it to work. Black's ...Nbd7 is a normal, sound move, so the trap costs nothing.
How to avoid it
e3 or Nf3, keep developing.