Overloading
A piece has too many defensive duties — attacking one of its tasks succeeds because it cannot answer two threats.
Overloading exploits a piece that is doing too much. A defender protecting two important squares or pieces can be attacked, forcing it to choose: if it defends one target, the other falls. The motif is sometimes described by saying the defender is overworked.
The clearest pattern is when a single piece guards both an important pawn and a critical square near the king. An attacker threatens the pawn; the defender must capture or block; the king is then unguarded; mate or massive material gain follows. The defender did its job — but only one of its two jobs.
Overloading is closely related to deflection and to removing-the-defender, but it differs from both in emphasis. Deflection is a single move that lures the defender away from its post. Removing-the-defender is a capture that eliminates the defender entirely. Overloading exploits the position before either of those steps: it diagnoses that the defender is already responsible for too much, and any sufficiently sharp threat forces a fatal choice.
Strong players evaluate every potential defender by counting its duties. A defender with one task is solid; a defender with two is suspect; a defender with three is usually a tactical opportunity waiting for the right setup.