It not only has the functions of traditional library, but also integrates some functions of other information resources (such as museums and archives). It breaks the limitation of national boundaries and time and space, and will become the public information center and hub of the future society.

At present, there is no unified and accepted definition of digital library. Some institutions and researchers put forward their own views from their own perspectives. For example, the American Information Infrastructure Technology and Application Working Group proposed in 1993 that the digital library is such a system that users can continuously access various information and knowledge bases to obtain materials. 1994 the electronic library project team of the university of California, Berkeley thinks that the digital library is a virtual library, that is, thousands of electronic libraries are connected together through the network, which is opaque to users, and users only see an all-inclusive library. The resource services provided by traditional libraries mainly include books, periodicals, newspapers, bibliographies, audio-visual materials and data retrieval. Online digital library also provides the same information service, and realizes the function of traditional library to a higher degree.