It can be best described like this.
ASMR is when you watch someone doing something and it intrigues you to the point that you get tingles. That's the best I can do with an explanation.
Same happens with music and videos.
I experience this sensation when I watch a ski movie with loud speakers or music that gets me really stoked.
there is a whole research project in the process going on right now.
http://www.asmr-research.org/