An institutional repository can be viewed as a set of services that a university offers to members of its community for the management and dissemination of digital materials created by the institution and its community members." For a university, this includes materials such as monographs, eprints of academic journal articles—both before (preprints) and after (postprints) undergoing peer review—as well as electronic theses and dissertations (ETDs).
An institutional repository might also include other digital assets generated by academics, such as administrative documents, course notes, learning objects, or conference proceedings. Deposit of material in an institutional repository is sometimes mandated by that institution.
Some of the main objectives for having an institutional repository are to provide open access to institutional research output by self-archiving it, to create global visibility for an institution's scholarly research, and to store and preserve other institutional digital assets, including unpublished or otherwise easily lost ("grey") literature such as theses or technical reports.
Source: Wikipedia. Read more at https://en.wikipedia.org/wiki/Institutional_repository