As part of the publishing process, authors may transfer all or selected rights to a publisher. The author keeps some rights by standard agreement, by using an addendum, or by negotiation. Most commonly, authors keep the right to self-archive a final author manuscript version (either before or after peer review). Sometimes there is an embargo.
In 2017, it was reported that 2,375 publishers (41 percent) allowed pre- and postprint versions of articles to be self-archived. 33 percent only allowed the self-archiving of the postprint--the final draft post-refereeing. 6 percent of publishers only allowed self-archiving of the preprint--the pre-refereeing draft.
Attitudes about sharing articles before peer review vary with disciplines and changes over time. Sometimes your publication agreement will require you remove preprints after peer review or update them to a postprint/final author manuscript version. You can check with the publisher or SHERPA/RoMEO or List of academic journals by preprint policy (Wikipedia)
The School of Medicine uses the Digital Commons@Becker repository. Arts & Sciences, School of Law, Brown School, McKelvey School of Engineering, Sam Fox School of Design & Visual Arts, and Olin Business School use Open Scholarship.