tooth root?

It's called abrasion. It can be from brushing too hard over years or other reasons. The dentin of your tooth (the dentin is what overlys the nerve of the tooth) is what you are seeing/feeling. By placing a sealant or some form of composite restoration over the area of exposure you will notice a decrease in sensitivity. Your dentist can also place Duraphat over the sensitive area to seal off the dentinal tubules to prevent the hot/cold liquids from irritating the tooth. Good luck!

Sounds like you are touching dentin which is under the enamel of your tooth. The roots of your teeth do not have enamel.

The dentin, if exposed, will be very sensitive to hot and cold.

It doesn't sound like you will need a root canal, but your dentist can place bonding material over the exposed area so that it will not be sensitive anymore.

This procedure is quick. You will notice a diffence right away!

Probably "dental cervical abrasion" or mild "dental abfraction," if you want to search these terms. You are not actually touching the nerve, but just the dentin, which is sensitive by mature. You'll find some explanation under the cervical abrasion search.

I don't know what it is. It sounds like something that only a dentist can identify.

If you don't want us to say that you should see a dentist, then why do you post a question with such an obvious answer?

It sounds like a cavity to me. I'd go see a dentist!

are you all there?