Overloading: One Piece, Too Many Jobs
The Overworked Defender
An overloaded piece is one that has been given more defensive jobs than it can handle. Maybe a single knight is guarding two different squares, or a queen is both defending a back-rank mate and protecting a loose piece. As long as nothing forces the issue, it looks fine — but it is stretched thin, and that is a weakness.
Make It Choose
The way to punish an overloaded piece is to attack or capture one of the things it defends. To deal with that, the defender must let go of its other duty. Whichever job it abandons, you cash in there. The piece simply cannot be in two places at once.
A Concrete Picture
Suppose the opponent’s queen is doing two jobs: it defends a bishop and it also guards the only square that stops a back-rank checkmate. You capture the bishop. If the queen recaptures, it leaves the back rank and you deliver mate. If it ignores the bishop to stay home, you are simply up a bishop. The queen was overloaded, so you win either way.
Overloading vs. Deflection
These tactics are close relatives. Deflection forces a piece off one specific duty. Overloading recognizes that the piece had too many duties to begin with, then exploits that by attacking a second one. In practice you find overloading by asking, is any enemy piece defending two important things at once? If so, hit the cheaper one and watch the structure collapse.