A front derailleur is a component of a bicycle's gear system that helps shift the chain between different front gears, or chainrings. It is typically mounted near the bottom bracket and is controlled by a lever on the handlebars. When activated, it moves the chain from one chainring to another, allowing the rider to change gears for easier pedaling or increased speed. The front derailleur works in conjunction with the rear derailleur, which shifts the chain across the rear gears. Together, they provide a range of gear options, enhancing the bike's performance on various terrains. Proper adjustment of the front derailleur is essential for smooth shifting and optimal riding experience.