It's like this. If you're burning something, in this case organic material, there's a variety of paths by witch you can arrive at the goal of burnt. In this particular instance we have a mixture of tobacco (shredded) and air inside an air barrier that is flammable, the flammability carefully calibrated chemically to achieve a desired rate of combustion. This factor is not a variable for our purposes, as it is controlled by the manufacturer. The air to fuel ratio of our desired combustibles however, presents a myriad of variety in how the composite chemicals of combustion are released. Whether they are vaporized or burnt is a huge factor. The air to fuel ratio is a measure of how much tobacco to how much air is inside the air barrier. The ratio can be manipulated by the compaction of the shredded tobacco resulting in more fuel, less air. The resultant varieties in release of the components of combustion is otherwise referred to as, 'flavor.'
You can also tell it's a thing by the fact that every manufacturer packages their cigarettes in such a way that, 'this end up' they ride in the truck and get compaction as opposed to loosening. The cases are clearly labeled...