Bicycle gears are mechanical systems that help cyclists adjust the resistance they feel while pedaling. By changing gears, riders can make pedaling easier on flat surfaces or increase power when climbing hills. Gears are typically found in the chainring at the front and the cassette at the back of the bike. The gear ratio, determined by the size of the chainring and the cogs on the cassette, affects how far the bike travels with each pedal stroke. Lower gears provide more torque for climbing, while higher gears allow for faster speeds on flat terrain. Understanding gears helps cyclists optimize their performance.