Abstract:  Many automated libraries in the country are stepping forward to create and maintain digital libraries. The traditional functions of libraries had undergone various changes in present century and e-resources have great importance in libraries and amongst the library users, because in today’s rapid changing world, information needs of learners and knowledge searchers are met through a plethora of sources. Preservation of digital information is a challenge because understanding the main activity in digital preservation i.e. ‘format of the document’ is difficult.  This paper discusses the types of digital resources, types of digital formats.  It includes brief summary on important file formats.