Atoms vibrate at varying rates according to a variable number of influences. Temperature being the most common example. However atomic makeup and other physical characteristics can alter these vibrations. It is theorized that everything gives off it's own unique vibration (similar to human bodies and finger prints!). These unique vibrations create a wavelike energy referred to as a "vibe". These energy signals can be detected and altered by beings with heightened extrasensory abilites. In humans, the Third Eye (controlled by the Pineal Gland) lets them use very primitive senses to get minor reads on these vibrations. Some beings may be able to feed on or alter the energy created. These energies are known to us also as aura(s). Otherkin have energy signatures that do not match their physical form due to the entity being in an entirely new physical form altogether... Just an idea I'm floating. Fester on it and see where that goes.