Essential oil: distilled via heat/water
Resinoid: single step solvent extraction usually of a dry material or resin. All kinds of different solvents can be used.
Absolute: two-stage solvent extraction, more often of fresh materials. The second solvent is always alcohol
Concrete: the first hexane extract produced in the two stage absolute production process. It is more or less like a resinoid but made from fresh plant material most often. Seems like hexane is almost always the preferred solvent for this process but others could be used as well.
A resinoid is produced by soaking the ground up wood in some kind of solvent (likely ethanol), then filtering and evaporating the solvent, leaving an oily residue. This will contain the essential oil, pigments, waxes, carbohydrates, all of the soluble materials in the wood regardless of whether they are evaporate easily and are aromatic or not. On average these resinoids tend to be darker colored, thicker, with different olfactory properties, but expert extractors can select different solvents to fine-tune how thick or sticky it is. generally the smell will be quite different from the distilled oil, and the transformation of the aroma over time will be different in terms of the character and the duration of the scent.
Essential oils concentrate only the materials that evaporate relatively easily and it is purely composed of volatile aromatic materials. In that sense it is a more concentrated extract than the resinoid and very often the essential oil will be more expensive because it has a significantly lower yield (the same is true for rose essential oil versus rose solvent extract).
Typically you might expect a resinoid to have a longer duration on skin but Sandalwood is a special case. Sandalwood essential oil is distilled in a particularly energy intensive way to concentrate some very heavy molecules known as santalols, and a steam distilled oil that meets specifications will be over 90% santalol. These have extremely good tenacity on skin and so steam distilled essential oil can last for 12 hours as a personal fragrance.
Because of the presence of waxes and pigments the resinoids will have a substantially lower percentage of santalol than the distilled oil, and because of that in the particular case of sandalwood the resinoids may actually have a shorter duration on skin. However in my experience they make up for this by having a very rich and saturated top and heart note bouquet. Like the volume can be 10 times more intense than a steam distilled oil. The candle that burns twice as bright burns half as long of course
(Other plants are generally not distilled in quite the same way that Sandalwood is, and they have lighter more volatile essential oils of shorter duration, and for those plants the resinoids may well have a longer duration because the waxes kind of act to retard the evaporation of the aroma)
