In computer science, instantiation is the realization of a predefined object. In OOP (object-oriented programming), a class of object may be defined. All objects of this class have a certain set of properties (associated variables), accessories (ways to access those variables), and methods (functions). An instance of that object may then be declared, giving it a unique, named identity so that it may be used in the program. This process is called "instantiation."
The term "instantiation" is also used in other areas of computer science, such as in the creation of virtual servers. The virtual server's properties (disk space, allocated RAM, type of operating system, installed software, etc.) are defined beforehand. Then, multiple servers can be virtualized on a single machine, each using that configuration. The process of virtualizing them is referred to as instantiation, and each virtual server is called an instance.