What types of hubs are there?

There are various types of bicycle hubs, including freewheel hubs, gear or internally geared hubs, and fixed-gear hubs. Freewheel hubs are the most common hubs and allow the cyclist to brake while pedaling by disengaging the drive mechanism from the hub. Gear or internally geared hubs have multiple gears and allow the cyclist to change the gear ratio by shifting the rear wheel into a different position. Fixed-gear hubs are specifically designed for fixed-gear bikes, where the rear wheel is directly connected to the pedal drive. Hubs can also be equipped with additional features, such as electric assistance from a motor or hub dynamo technology that powers the bicycle's lighting.