Digital library is a term and concept that serves as an umbrella for a great many of diverse activities. We can also call it Virtual library, electronic library, library without walls. "Digital libraries are organized collections of digital information. They combine the structure and gathering of information, which libraries and archives have always done, with the digital representation that computers have made possible. "A digital library is a managed collection of information, with associated services, where the information is stored in digital formats and accessible over a network. "Digital libraries are organizations that provide the resources, including the specialized staff, to select, structure, offer intellectual access to, interpret, distribute, preserve the integrity of, and ensure the persistence over time of collections of digital works so that they are readily and economically available for use by a defined community or set of communities.

We interpret digital libraries and all the associated activities in a broad sense as to encompass great many variations on two general themes of (i) organizing and accessing human knowledge records in (ii) digital and networked environments. More often than not, this understanding is an implicit rather than an explicit assumption in the majority of works claiming to deal with digital libraries. The first of the two underlying themes is not new, of course. Collecting, organizing, preserving, and accessing human knowledge records were themes of many efforts from the dawn of civilizations, across time, cultures, geographic boundaries, and societies. It is a permanent theme, because the evolution and functioning of any advanced society is connected with creation and use of a societal memory through records. Conventional catalogs and indexes, whether created manually or by automatic indexing, are ill suited for searching heterogeneous content with highly varied metadata.  Fortunately, the power of modern computing that makes large-scale digital libraries possible also supports new capabilities for information discovery. Given that understanding and the advances in capabilities of digital and network technologies, it is not surprising that digital libraries draw a lot of interest. The history of digital library is short and explosive. A number of early visionaries, such as Licklider (1965), had a notion of libraries in the future being highly innovative and different in structure, processing, and access through heavy applications of technology. But, besides visionary and futuristic discussions and highly scattered research and developmental experimentation, nothing much happened in the next two decades. By the end of the 1980s, digital libraries (under various names) were barely a part of the landscape of librarianship, information science, or computer science. But just a decade later, by the start of 2000s, research, practical developments, and general interest in digital libraries has exploded globally. What a decade for digital libraries!