Instantiation is the process by which a C++ compiler creates a usable function or object from a template. The C++ compiler uses compile-time instantiation, which forces instantiations to occur when the reference to the template is being compiled.
The advantages of compile-time instantiation are:
Debugging is much easier. Error messages occur in context, allowing the compiler to give a complete traceback to the point of reference.
Template instantiations are always up-to-date.
The overall compilation time, including the link phase, is reduced.
Templates can be instantiated multiple times if source files reside in different directories or if you use libraries with template symbols.