[د.محمود قطر]

A library is a collection of information resources and services, organized for use, and maintained by a political body, institution, or private individual. In the more traditional sense, it meant a collection of books. This collection and services are used by people who choose not to — or cannot afford to — purchase an extensive collection themselves, who need material no individual can reasonably be expected to have, or who require professional assistance with their research.
However, with the collection of media other than books for storing information, many libraries are now also repositories and access points for maps, prints or other artwork, microfilm, microfiche, audio tapes, CDs, LPs, cassettes, video tapes and DVDs, and provide public facilities to access CD-ROM and subscription databases and the Internet. Thus, modern libraries are increasingly being redefined as places to get unrestricted access to information in many formats and from many sources. In addition to providing materials, they also provide the services of specialists who are experts in matters related to finding and organizing information and interpreting information needs, called librarians.
More recently, libraries are understood as extending beyond the physical walls of a building, by including material accessible by electronic means, and by providing the assistance of librarians in navigating and analyzing tremendous amounts of knowledge with a variety of digital tools.
The term 'library' has itself acquired a secondary meaning: "a collection of useful material for common use", and in this sense is used in fields such as computer science, mathematics and statistics, electronics and biology.

المصدر : ويكيبيديا (النسخة الإنجليزية) على الرابط
http://en.wikipedia.org/wiki/Library