Null literally means "null" in English. This term is used mainly in computer language, in the areas of computer science, especially in programming, to represent something without a set value.
In computer programming, null represents a special value for a null object reference. In programs written in the C language, 0 is used as null, since almost all operating systems consider it an error to access an address with this value.
In some programming languages, like Delphi, LISP, and Pascal, null is also called variant null or nil.
Null in Operating Systems
On some operating systems, such as Unix, DOS and Microsoft Windows, null is considered a reference to a device that is null, that is, a special file that erases data sent to it and does not return data to the processes.
For some parts of computer science, null is also indicated as unknown value, for example, the database SQL, O Visual Basic, and etc.
Learn more about meaning of SQL.