When I scratch my cat in certain places she tends to go “crazy”. Crazy as in: she’ll bob her head up and down or side to side quickly, she’ll open and close her mouth quickly, and she’ll start licking the closet object to her face aggressively. I’ve also noticed that there are little bumps in the certain areas I scratch her. She stays in place and goes crazy, when shes going crazy it seems like she has no control over herself.
I think it is intense pleasure you know the feeling of having an itch you can not reach and the feeling of getting help hitting the right spot.
Many cats react like yours when they are getting brushed too. They lose control and can start licking you and start kneading you. Some start to bite and are chewing on your hand and fingers.
This is what I think is going on and many cats react like this.
A little warning: some cats really hate getting brushed. If this happens you need to brush your cat for a shorter time and give your cat a break before you try again. Most cats will get used to brushing after some time.
As far as I can tell, there is no universally accepted word for it, but many cat owners have discovered "That Spot" on their cat and come up with their own word for it. The term that seems to be the most prevalent that I've heard is "lick button." It seems to be a point that somehow causes an automatic reflex in cats when touched there, similar to the spot just below your knee that a doctor will tap to stimulate a kicking reflex. As far as I can tell, it's been little researched, and so I cannot say if this "reflex" is caused by the same mechanism that causes the kicking reflex, however. An example of "the lick button" can be seen in this video https://www.youtube.com/watch?v=fpG1xKN4ofo
On https://ask.metafilter.com/21558/Why-does-my-cat-spaz-out-when-I-touch-her-in-a-certain-spot a former breeder claims that this spot is "is an "accupressure" spot connected to the cat's sex response system," and that breeders will apply pressure to that spot to get their queens out of heat faster.