The air-filled or pneumatic tire is composed of a core filled with airtight sealed pressurized air. Typically, a reinforced steel belted tread or other materials, provides the contact area with the road and seals this inner core.
Because the pressure of the air inside the tire is more than atmospheric air pressure, the tire remains inflated even with the weight of the vehicle resting on it. The air pressure within the tire gives resistance against forces which try to deform the tire. This gives the tire a slight degree of a cushioning effect as the tire hits bumps in the road. If you have ever taken a ride in an old-fashioned carriage which had wooden wheels, you know how huge of a difference a set of pneumatic tires could make.
Of course, there are some drawbacks to pneumatic tires. For example in high-performance situations or highly dangerous applications, these tires could suffer a puncture and this would result in a total failure. The consequence of a blowout at high speeds can result in a dangerous car accident. Military planners must consider tires getting blown out by explosion shrapnel or shooting of guns. A vehicle crew's worst nightmare is becoming trapped within a fire zone because of all of their tires becoming flat. Airless tires evidently don't suffer from these issues and thus, may be more suitable in some applications.
Pneumatic tires have another problem involving variations in tire performance and air pressure. Lower tire pressure could create improved traction and increased comfort. This is because of the fact that tires flatten slightly and more tread is placed in contact with the road. The pressure of the air in the tire works to maintain the "up and down" stiffness as well as maintain the lateral stiffness of the tire. Hence, reduced air pressure enables the sidewalls of the tires to flex. This results in poor handling unfortunately. Within an airless tire, the stiffness in those two dimensions is independent.
There are other issues with air pressure. Consumers are notoriously unreliable when it comes to maintaining correct air pressure. Tires which have wrong air pressure can lead to dangerous situations. It is essential to keep in mind that pneumatic tires are also susceptible to temperature changes, that can be responsible for changing the internal tire pressure. It is very important to take into account the kind of environments you would be requiring your machine to function in so that you can inspect the tires regularly and keep the machine as safe as possible.