The pulp is soft tissue inside your tooth that contains nerves, blood vessels and provides nourishment for your tooth. It can become infected if you have a deep cavity, repeated dental procedures that disturb the pulp, a cracked or fractured tooth or an injury to the tooth. If this happens to you, your dentist may recommend a root canal. Root canals are done to repair and save your tooth instead of removing it.
If untreated, the tissues around the root of your tooth can become infected. When this happens, you will often feel pain and swelling and an abscess may form inside the tooth and/or in the bone around the end of the root of the tooth. An infection can also put you at risk of losing your tooth completely because bacteria can damage the bone that keeps your tooth connected to your jaw.
Your dentist will remove the infected pulp tissue, clean out the root canals and fill it with new material to seal the tooth and protect it from future infection. Once the root canal has been completed, you'll most likely need a permanent restoration like a filling or a crown to ensure long-term
If your case is more involved, you may be referred to a dentist who specializes in root canals. This specialist is known as an endodontist.
Source: American Dental Association