THC is absorbed into your lungs through the hemoglobin in blood. For this to replace oxygen and carbon dioxide (the usual gas exchange), the THC has to be more attracted to blood than one or both of those two gasses.

Next, the THC is carried through your blood, to your brain, where your cannabinoid receptors are waiting for it.

THC is then used by your cannabinoid system to calm down nerves that are acting strangely(Euphoria), and to make thoughts flow more easily.(Creativity boost)

Hope that helped.