An Institutional Repository (IR) is an online database that collects, preserves and publishes articles and other scholarly materials produced by an institution. Most IRs are maintained and promoted by universities or other research institutions, and collect the products produced by the scholars that the institution supports. Most IRs are open access as well, allowing anyone to read, download, and use the material collected therein for academic or other non-commercial purposes.
Just as the Open Access movement arose in part as a response to growing database subscription costs, Institutional Repositories have developed in part out of institutions realizing they were paying for research to be conducted and then having to rent back the fruits of that research (published articles, data sets, etc.) by purchasing (temporary) access to these articles from journal and database providers.
Some government and academic institutions have gone so far as to require that all articles produced using institutional funding be made (sometimes after a short embargo) openly accessible via their own or another institutions IR, thus ensuring that research that an institutions’ members, which in the case of a government is taxpayers, pay for is available to those members.