A TANDEM bike is a type of bicycle designed for two people, with both riders pedaling in unison. It typically has two sets of handlebars and two seats. A DIRT bike is a type of motorcycle designed for off-road riding on rough terrain. It usually has a lightweight frame and knobby tires for better traction. A ten-speed bike is a type of road bike with multiple gears, allowing the rider to adjust the level of resistance while pedaling.