Root canal treatment (RCT) and endodontic treatment are the more correct terms for a procedure that treats the nerve of the tooth.

Why Root Canal is necessary ?

If a tooth has become abscessed, it will require a root canal. An abscess is an infection that forms when the pulp of the tooth dies and a pus pocket forms around the end of the root.

If tooth decay extends deep into the tooth and reaches the pulp, the pulp will become infected with bacteria. When this happens, it will either become inflamed and painful or it will die and become decayed tissue.

There are many things that can damage the pulp or nerve of the tooth. Often a patient will feel pain or other symptoms that alert them to needing root canal treatment. The common reasons for needing root canal treatment are -

A toothache is the most common symptom of needing a root canal.
Jaw pain can either be an indication of pain in the jaw joint or pain referred from a tooth needing a root canal.
gum disease can mimic the throbbing pain around teeth that can feel similar to root canal pain

When the root canal is treated, the dental pulp is removed and all the canals and pulp chamber of the tooth are filled and sealed to prevent bacteria from entering.