Bike geometry refers to the measurements and angles that define a bicycle's frame and overall design. Key aspects include the length of the top tube, seat tube angle, head tube angle, and wheelbase. These dimensions influence how a bike handles, its stability, and the rider's position. Different types of bikes, such as road bikes and mountain bikes, have distinct geometries tailored for their intended use. For example, road bikes typically have a more aggressive geometry for speed, while mountain bikes feature a slacker angle for better control on rough terrain. Understanding bike geometry helps riders choose the right bike for their needs.