Hello Pankaj,
Just for ur Knowledge

I would like to know the difference between a
virtual library and a digital library.

A Digital Library is a repository of information in digital form, ie. Stored as
data files on a computer. It is also the tool-set provided to enable search and
retrieval of the repository.

The term "Electronic Library" is often used to mean much the same thing.

Another term frequently heard is "Virtual Library", which refers to a collection
of resources available on one or more computer systems, where a single interface
or entry point to the collections is provided. The key point being that the user
need not know where particular resources are located -- the location is
"virtual".