A root canal (endodontics) is performed by removing the nerve of the tooth and inserting a post. An impression is made for the crown which is cemented over the post.
The dentist drills through the tooth and pulls out the nerve under it. Then they will grind the tooth down and place the cap on top of that tooth stump.
After your gums have been numbed the dentist will drill through the center of your teeth. He then extracts the roots out so you have no more feeling in your tooth. Finally he cements a cap onto your tooth.