A pneumatic or air-filled tire consists of an inner core that is sealed airtight and filled with pressurized air. Typically, a tread made with reinforced steel belting or other materials, provides the contact area with the road and seals this inner core.
Since the pressure of the air in the tire is more than atmospheric air pressure, the tire remains inflated even with a vehicles' weight resting on it. The air pressure inside the tire provides resistance against forces which attempt to deform the tire. When the tire hits bumps in the road, this gives the tire a slight degree of a cushioning effect. If you have ever taken a ride in an old-fashioned carriage which had wooden wheels, you know how big of a difference a set of pneumatic tires makes.
Of course, there are some drawbacks to pneumatic tires. For instance in highly dangerous applications or high-performance situations, these tires could suffer a puncture and this will lead to a complete failure. The consequence of a blowout at high speeds could lead to a dangerous car accident. Military planners must take into consideration tires getting blown out by explosion shrapnel or gunfire. The worst nightmare of a vehicle crew is becoming trapped in a fire zone because of all of their tires becoming flat. Airless tires obviously don't suffer from these problems and hence, in certain applications, may be more suitable.
The pneumatic tire may have issues as well with the variation in air pressure and tire performance. The lower pressure in a tire may increase the traction and the comfort level. This is due to the fact that tires flatten slightly and more tread is touching the road. The pressure of the air inside of the tire works to maintain the lateral stiffness of the tire as well as maintain the "up and down" stiffness. Hence, reduced air pressure allows the tires' sidewalls to flex. Unfortunately, this results in poor handling. In an airless tire, the stiffness in those two dimensions is independent.
There are other issues with air pressure. Consumers are notoriously undependable when it comes to maintaining proper air pressure. Tires which have improper air pressure can result in unsafe situations. It is important to note that pneumatic tires are also susceptible to temperature changes, which can be responsible for changing the internal pressure of the tire. It is important to consider the type of environments you will be requiring your machinery to function in so that you could check the tires regularly and keep the machinery as safe as possible.