ASMR is an experience characterized by a static-like or tingling sensation on the skin that typically begins on the scalp and moves down the back of the neck and upper spine. It has been compared with auditory-tactile synesthesia and may overlap with frisson.
It is estimated that only 10-20% of the human population experience ASMR, so if you are in that group then you can be considered very lucky!
There are MANY 'triggers' (ways which ASMR is activated) and it is unique to the person. Some may find that listening to other people whisper activates the tingles, for others it could be slow, visual hand movements.
Those who do not understand may find watching ASMR videos strange, simply because they cannot relate to the relaxing effect it has as well as the tingling sensation.