Defining "born digital"

OCLC published “Defining Born Digital” which is a short 4-page intro, and isn’t in any way meant to be comprehensive. The document doesn’t (and can’t without being much longer) begin to address many areas and doesn’t include references for further reading.
For anyone interested in working with born digital materials, publications from the Electronic Literature Organization (ELO) are essential reading:

These publications are essential because electronic literature defines and redefines “born digital”. Electronic literature does so a highly experimental creative form that pushes the boundaries of existing technologies, creates new technologies, and uses/connects technologies in new ways that creates new conceptual ways of working and that is radically changed. Standard methodologies for normal born digital files don’t necessarily or simply don’t apply. By defining what can be done, electronic literature  serves as a forcing function that defines born digital materials and how to address them in terms of practices, methods, and tools for all stages of the digital lifecycle.
The Electronic Literature Organization’s (ELO) publications are also essential reading because they explain the human requirements, which are part and parcel with technical requirements:

The long-term preservation of digital works—and especially of complex or experimental e-lit works that test the limits of new media—will require the labor of many stakeholder communities (authors, readers, editors, teachers, publishers, librarians, programmers) that presently do not have excellent means of coordinating with each other. Establishing a framework that can allow for the commitment of time and resources from distributed sources without everyone needing to reinvent the wheel is what the creation of standards—especially open source standards—is all about.
In its role as one of the few organizations representing electronic literature—and the only one focused on the breadth and history of such literature—ELO can initiate the building of such a standards-based framework in alliance with university, library, and other institutions. (Born-Again Bits)

Acid-Free Bits and Born-Again Bits are essential first readings but are by no means all that ELO has to offer. ELO has many other excellent publications and resources, including the especially wonderful resource of members who are actively working with born digital concerns as well as assisting (and being available to assist) others in doing so.