The term "id" has multiple meanings depending on the context. In psychology, the id is one of the three agencies of the human personality, along with the ego and superego. It is the oldest of these psychic realms in development and contains the psychic content related to the primitive instincts of the body, notably sex and aggression, as well as all psychic material that is inherited and present at birth.
In everyday language, "id" is often used as an abbreviation for "identification." An identity document (ID) is any document that may be used to prove a persons identity. If issued in a small, standard credit card size form, it is usually called an identity card (IC, ID card, citizen card), or passport card. Some countries issue formal identity documents, as national identification cards that may be compulsory or non-compulsory, while others may require identity verification using regional identification or informal documents.
In addition, "ID" can also refer to a means of identification, such as a card or bracelet containing official or approved identification information.
