MEDID, or medical identification, is an identification system based on a unique number assigned to a person who is undergoing medical treatment or observation. This number helps keep track of medical information, data, and files related to that individual. It is also used to help protect patient privacy and to avoid medical errors. The 318 part specifically refers to the specific code assigned to each individual person. The code is generally a combination of alpha and numeric characters and is used to help quickly identify a patient. Additionally, the code helps to eliminate any confusion between different treatments or care providers for a patient.