There are many types of surgery just as there are many varieties of illness or injury.  Although there are some ailments which cannot be or do not need to be treated by surgery, most of the problems the human body encounters can be corrected through a combination of medicine, therapy and surgery procedures.  Surgeries are usually categorized by the region of the body they are conducted on and the degree of invasion or difficulty that is involved.  Further classifications take into account the degree of importance of the surgery - life-threatening versus elective surgery is the usual division.

Elective surgery is common, generally because all the operations and surgical procedures which are not used to correct life-threatening problems are classed as elective.  Elective surgery includes cosmetic surgery (such as breast enlargements or liposuction) and some corrective surgery (such as laser eye surgery).  These types of procedures are usually undertaken at the request of the patient.

Far more serious is emergency surgery, particularly because it is done under the pressure of time and sometimes horrible conditions. 

Emergency surgery is usually carried out because a patient has been presented with a life-threatening illness or injury which may or may not have been diagnosed.

In between elective and emergency surgery in terms of the importance to the patient's health is the third classification, exploratory surgery.  This type of procedure usually occurs because the doctor or specialist suspects that there may be a problem or issue which is contributing (or may contribute in the future) to a decline in the patient's well-being. 

Exploratory surgery aims to get closer to the potential problem so as to determine if there is something there to be corrected.