The air in bicycle tires serves primarily as a cushion that absorbs uneven terrain. Every little stone and crack in the asphalt could damage a solid tire. The tire, when filled with air, simply absorbs the shock, and continues to roll.
Bicycle tubes come in different sizes and varieties. You will find inner tubes for children's, road, gravel, city and mountain bikes. When ordering new bicycle inner tubes, you must make sure that they are the correct size. In addition, the valve must fit your rims otherwise it will not fit in the rim hole. There are bicycle tubes made of different materials and from different manufacturers.