ID is the abbreviation of English IDentity, which means identification number. It is called serial number and account number, which is a code and unique. Equivalent to an ID card. In a specific matter, its ID number is unchanged. As for what to use to identify that thing, it is determined by the rules formulated by the designer. This rule has certain subjectivity, such as employee job number, ID number, computer website, port number and so on.

For computers, there are two operation modes, logical operation and arithmetic operation. For logical operations, it is the ID function of numbers. Of course, ID is actually very common in life. For example, if you stick the product model and production number on something similar to distinguish them, this is also called ID.