What is a polarized extension cord

Power Strip Extension Cord 3 Outlets 3m Swing Plug Polarity Compatible PSE Technical Standards Compliant White (N-Pole Compatible) ECT-4030WH

2 Piece SAE Polarity Adapter for Extension Cord Maintainer Black

Power Strip Extension Cord 3 Outlets 3m Swing Plug Polarity Compatible PSE Technical Standard Compliant Black (N-Pole Compatible) ECT-4030BK

Power Strip Extension Cord 3 Outlets 5m Swing Plug Polarity Compatible PSE Technical Standards Compliant White (N-Pole Compatible) ECT-4050WH

Power Strip Extension Cord 5m 1 Outlet with Dust Prevention Shutter Polarity Compatible Plug Connection Swing Plug Thermosetting Resin Black

Power Strip Extension Cord 3 Outlets 5m Swing Plug Polarity Compatible PSE Technical Standards Compliant Black (N-Pole Compatible) ECT-4050BK

Power Strip Extension Cord 5m 1 Outlet with Dust Prevention Shutter Polarity Compatible Plug Connection Possible Swing Type Plug Thermosetting

Power Strip Extension Cord 3m 1 Outlet with Dust Prevention Shutter Polarity Compatible Plug Connection Possible Swing Type Plug Thermosetting

Power Strip Extension Cord 3 Outlets 2m Swing Plug Polarity Compatible PSE Technical Standards Compliant White (N-Pole Compatible) ECT-4020WH

ELECOM Power Tap Extension Polar Plug Swing Plug Cord, 1m, Dust-proof Shutter, Compatible, 3-Pin Connectable, Black, T-X01-2110BK

Power Tap Extension Dust Prevention Polar 3 Pin Plug White Cord, 2m, Shutter, Compatible, Connectable, T-X01-2120WH