Chess tactic
In chess, a decoy is a tactic that lures an enemy ;dfn id="" ;man ;/dfn ; off its square and away from its defensive role. Typically this means away from a square on which it defends another piece or threat. The tactic is also called a "deflection". Usually the piece is decoyed to a particular square via the sacrifice of a piece on that square. A piece so sacrificed is called a "decoy". When the piece decoyed or deflected is the king, the tactic is known as attraction. In general in the middlegame, the sacrifice of a decoy piece is called a "diversionary sacrifice". 
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Examples.
The game Honfi–Barczay, Kecskemet 1977, with Black to play, illustrates two separate decoys. First, the white queen is set up on c4 for a knight fork: 
1... Rxc4! 2. Qxc4
Next, the fork is executed by removing the sole defender of the a3-square: 
2... Qxb2!+ 3. Rxb2 Na3+ 4. Kc1
Finally, a zwischenzug decoys (attracts) the king to b2: 
4... Bxb2+
After either 5.Kxb2 Nxc4+ 6.Kc3 Rxe4, or 5.Kd1 Nxc4, Black is two pawns ahead and should win comfortably.
In this position, after the moves 1.Rf8+ Kxf8 ( ;dfn id="" ;forced ;/dfn ;) 2.Nd7+ Ke7 3.Nxb6, White wins the queen and the game. A similar, but more complex position is described by Huczek. 
In the diagrammed position from Vidmar–Euwe, Carlsbad 1929, Black had just played 33...Qf4, threatening mate on h2. White now uncorks the elegant combination 34.Re8+ Bf8 (forced) 35.Rxf8+ (attraction) Kxf8 (forced) 36.Nf5+ (discovered check) Kg8 (36...Ke8 37.Qe7#) 37.Qf8+ (attraction) 1–0 Black resigns. (If 37...Kxf8 then 38.Rd8#. If 37...Kh7 then 38.Qg7#.) The combination after 33...Qf4 features two separate examples of the attraction motif.
This example shows a position from the game Dementiev–Dzindzichashvili, URS 1972. White had just played 61.g6 (with the threat 62.Qh7+ Kf8 63.Rxf5+). However, Black continued with the crushing 61...Rh1+ (attraction) 62. Kxh1 (best) Nxg3+ (the white rook is pinned) 63.Kh2 Nxh5 and White has dropped his queen to the knight fork. In the game, White resigned after 61...Rh1+.
Perhaps the most celebrated game featuring a decoy theme is Petrosian–Pachman, Bled 1961, which also involved a queen sacrifice. Pachman resigned after 19.Qxf6+ (attraction) Kxf6 20.Be5+ Kg5 21.Bg7! setting a ;dfn id="" ;mating net ;/dfn ;. 
In the game Menchik–Graf, Semmering 1937, Graf resigned after 21.Rd7, deflecting Black's queen. (If 21...Qxd7, then 22.Qxh5 with mate to follow; 21.Qxh5 immediately wins only a pawn after 21...Qxh2+.) 
Often a ;dfn id="" ;wing ;/dfn ; pawn serves as a decoy in endgames. In the game Ivkov–Taimanov, Belgrade 1956, Black resigned in the position shown because White has an easy win by using his passed a2-pawn as a decoy to ;dfn id="" ;lure ;/dfn ; Black's king away from the ;dfn id="" ;center ;/dfn ; and to the ;dfn id="" ;queenside ;/dfn ;, allowing easy promotion of the h6-pawn.
References.
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Bibliography