Linked from
The 9 pages that link to Bicycle chain, each with the reason it gives.
BicycleBroader topic: It is the common mechanical link between pedals and rear wheel.
Bicycle gearingRelated: The chain couples the selected front and rear toothed wheels.
Bicycle drivetrainRelated: It carries motion from the front chainring to the rear sprocket.
DerailleurRelated: The derailleur shifts this flexible loop without disconnecting it.