In programming, instantiation is the creation of a real instance or particular realization of an abstraction or template such as a class of objects or a computer process. To instantiate is to create such an instance by, for example, defining one particular variation of object within a class, giving it a name, and locating it in some physical place.
1) In object-oriented programming, some writers say that you instantiate a class to create an object, a concrete instance of the class. The object is an executable file that you can run in a computer.
2) In the object-oriented programming language, Java, the object that you instantiate from a class is, confusingly enough, called a class instead of an object. In other words, using Java, you instantiate a class to create a specific class that is also an executable file you can run in a computer.
3) In approaches to data modeling and programming prior to object-oriented programming, one usage of instantiate was to make a real (data-filled) object from an abstract object as you would do by creating an entry in a database table (which, when empty, can be thought of as a kind of class template for the objects to be filled in).