What is a fixie bike and how does it differ from other types of bicycles?

A fixie bike, short for fixed-gear bike, is a type of bicycle that has a single gear and no freewheel mechanism, meaning the pedals move in sync with the wheel. This design allows for direct control over speed and requires the rider to constantly pedal, even when going downhill. Fixie bikes are known for their simplicity, lightweight design, and responsiveness, making them popular among urban cyclists and bike enthusiasts. They differ from other types of bicycles, such as geared bikes, which have multiple speeds and freewheel mechanisms that allow the rider to coast without pedaling.