Though not an opening trap this trap is good and instructive.
It's a genuine trap because it carries a risk.
The risk can be positional or material, but a pure chess trap means you
have shunned better moves to set your trap.
Good moves that carry hidden threats are not traps. They are good moves.
The only real justification for playing a genuine trap is if you are losing.
However, having written that it won't stop me from setting traps
(because I'm good at it. 😉) and, more to the point, I enjoy it.
In the following game White should have lost a piece in setting his trap,
instead he wins a Queen. He has trap-setters luck (there is such a thing)
I predict a bright future for this lad.
TK80 - BIGBADBOB1 RHP 2012
[FEN "r1b1kbnr/pppq1ppp/3p4/3Np3/2BnP3/3P1N2/PPP2PPP/R1BQK2R w KQkq - 0 7"]
7. a4 {White builds his trap. The move 1.a4 was aimed at the coming 1..c6.} 7... c6 {And there it is.} 8. Nxd4 exd4 {Now to set the trap White needs a throw away move. Anything to give Black back the move.} 9. Bf4 {And he chooses a bad move. (see next bit) Castles would have been a good waiting move.} 9... cxd5 {Black falls for it.} 10. Bb5 {Pins and wins the Queen and now we see the idea behind 1.a4. That is how the game went and Black resigned. 1-0}
What should have happened.
[FEN "r1b1kbnr/pp1q1ppp/2pp4/3N4/P1BpP3/3P4/1PP2PPP/R1BQK2R w KQkq - 0 9"]
9. Bf4 {This was White's chosen tempo loser. It should have lost a piece. Now instead of taking the Knight....} 9... Qd8 {...The Queen comes off the critical diagonal and prevents Nc7+ So the d5 Knight has to move and Thanks to Bf4 the Knight has only one square to go to.} 10. Nb4 d5 {Hits the c4 Bishop and the b4 Knight. White losses a piece.}