Elephant Trap is the trap for White that occurs in a popular variation of Queen's Gambit Declined. White pins the Black's f6 knight and captures the d5 pawn not realizing that it's actually them who blundered and about to lose a piece, and most likely a game. It is a 'must to know' trap to have in your repertoire if you are a d4 player or/and if you often face 1.d4.
Not only it will help you win some online blitz games, but it also can trick an unaware yet greedy over the board opponent and bring you an easy win. It also helps to know the classical traps so that you don't become a victim of one and lose a game prematurely without the fight..It's never good.
You can scroll the trap's move, read the annotation and see the diagrams below:
The game starts as a standard Queen's Gambit Declined
1. d4 d5
2. c4 e6
3. Nc3 Nf6
4. Bg5 Nbd7
The d5 pawn is being attacked 2 times but defended only once due to the pin on f6 knight
Here white probably expected something like 4...Bd7 or 4...c6 defending the d5 pawn. But Black plays a tricky move 4...Nbd7 setting up the trap. White doesn't realize it and just believes that Black is careless and giving up a pawn. The key position is presented on the diagram below. The d5 pawn is being attacked twice but defended only once since the f6 knight is pinned to the queen. Therefore, it looks like white can win the d5 pawn.
5. cxd5 exd5
after 6. Nxd5?? white loses a minor piece
White initiates the exchange in the center seeing that there are more attackers than defenders. However, it is a blunder and the trap comes into play.
Black captures the d5 knight ignoring the pin on the Queen. At this point regardless what White plays they already will be down material.
7. Bxd8 Bb4+
That's exactly what White missed: the King is trapped by its own pieces and cannot escape check, the only legal move is to interpose with the Queen.
8. Qd2 Bxd2+
Deadly check 7...Bb4+
Black takes the Queen first with the check and only then captures the bishop.
9. Kxd2 Kxd8 Black is much better here and easily wins the game