The Zotero website has more details of this open-source software programme.
There are a number of LibGuides by other institutions on Zotero: an excellent example is by Jason Puckett of Georgia State University.
Zotero is a project of the Corporation for Digital Scholarship - "a non-profit organization dedicated to the development of software and services for researchers and cultural heritage institutions." (Corporation for Digital Scholarship, 2019).
Screenshots are chiefly of Zotero programme in use: other screenshots are from databases subscribed under license to the University of Birmingham:
Web of Science: Clarivate Analytics
Ovid databases including Medline: LWW Wolters Kluwer
Proquest databases including Nursing and Allied Health: Proquest
EBSCO databases including CINAHL, Business Source Premier and others: EBSCO Publishing