A freehub is a crucial component of a bicycle's rear wheel, allowing the rider to coast without pedaling. It consists of a ratcheting mechanism that engages when pedaling forward and disengages when coasting. This design enables the bike to move freely without constant pedaling, making it easier to ride downhill or on flat terrain. Freehubs are commonly found on modern bicycles, especially those with cassette systems. They come in various designs and sizes to accommodate different types of bikes, such as mountain bikes and road bikes. Proper maintenance of a freehub is essential for smooth operation and longevity.