You get anaesthesia, then the nerve in the tooth is basically ripped out. Then comes cleaning and shaping the root canal which for me at least often was painful

You get anaesthesia, then the nerve in the tooth is basically ripped out. Then comes cleaning and shaping the root canal which for me at least often was painful when the file basically poked into the tissue (and nerve) underneath the tooth. That's also the part that hurt for weeks after I had the procedure.