A bicycle inner tube is the tire installed inside the wheel. Together with the outer tire, it forms the wheel and provides support and cushioning. Inner tubes are typically composed of rubber and ply layers, with a reinforcing layer on top to increase their strength. The outer tire, on the other hand, is the tire installed outside the inner tube. Together with the inner tube, it forms the wheel and provides support and cushioning. The outer tire is typically composed of rubber, ply layers, and a tread, with a reinforcing layer on top to increase its strength.
Due to their different structures, bicycle inner tubes and outer tires differ significantly. Inner tubes are softer, providing excellent vibration damping, and are thinner, reducing rolling resistance; while outer tires are stiffer, offering better support, and are thicker, increasing grip.
If your bicycle only has one tire, it's likely an outer tire. Inner tubes are generally used when there is no outer tire; they are usually used in conjunction with the metal parts on the rim to provide better support and cushioning.
