How is dynamic equilibrium related to vapor pressure?
Vapor pressure is the observed effect of molecular motion.
Dynamic equilibrium is the observed state when all motion in a system is equally distributed - no "change" is observable. The motion of molecules is the action that creates the observed phenomenon of vapor pressure.
Thus, at any value of dynamic equilibrium a particular vapor pressure will be observed for a compound. Changing the conditions (heat or pressure) will change the dynamic equilibrium and thus also the vapor pressure observed. This is related to the development of the Ideal Gas Laws and the vapor pressure of liquids and solids.