ASMR is a pleasant tingling sensation in the skull due to a visual, auditory, olfactory or cognitive stimulus. For example, you may experience it when you go to the hairdresser. It began to be popular in 2010.
It’s a scientific phenomenon but we don’t know much about it yet. The first published study on the subject dates from 2015. Beware, this has nothing to do with sex.
ASMR is often used for relaxation. This technique has the power to relax and reduce stress levels. It also facilitates sleep. It boosts dopamine which is also called the happiness hormone.
Here is an example of ASMR. But you will find many others on the internet.