What is Surgery?

According to Wikipedia, surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance. There are many specific fields/specialties of surgery and surgeons. Some of the most famous fields include cardiac/cardiothoracic surgery, which deals with the heart and lungs, neurosurgery, which deals with the brain and the nervous system, orthopedic surgery, which deals with bones and joints, ENT surgery, which deals with the ears, nose, and throat, and plastic surgery, which deals with the appearance of a human being. Here is a diagram that shows a visualization of a open heart surgery, where the chest is opened and the sternum is cut.

Here is a diagram of a craniotomy, which is a form of brain surgery, where the surgeon removes part of the skull bone and cuts into the dura mater.