RE: What is it that creates the smoke?
Smoke is defined as particulate matter, suspended in gas.
It is very small solid, or liquid particles; such as ash from the different oils burnt in the engine and unburnt carbon, or unburnt liquid matter.
All fuel enters the engine in a liquid state and most of it becomes gaseous, before and during combustion.
But all combustibles must break-up into their elements before combustion and carbon has a much higher propensity to remain unburnt and thus leave the engine in its solid form, hence particulates - smoke.
And as to smoke emitted intentionally; it is particles of ash from burning and evaporation of special, low-viscosity oil, such as Chevron/Texaco "Canopus 13".
Water vapor, or fuel vapors are not smoke.