Zotero is a free and open-source reference management software. Modern reference managers like Zotero serve several functions at once. They make it easy to record citation information about documents that may prove useful in a research process, they provide a place to store downloaded PDFs and other documents, they serve as a note-taking platform, they facilitate creating citations in the correct style for a given project, and they store research information securely both on a users computer and in the cloud.
The Law Library's guide, Zotero for Legal Scholars, outlines the installation and use of Zotero.