BibTeX is a file format used for lists of references for LaTeX documents. Many citation management tools support the ability to export and import lists of references in .bib format. Some reference management tools can generate BibTeX files of your library or folders for use in your LaTeX documents.
Creating & Managing Bibliographies with BibTeX on Overleaf
LEARN HOW TO create and manage bibliographies using BibTeX on Overleaf by reading this article by Overleaf TeXpert, Lian Tze, that pulls together all the threads relating to citations, references and bibliographies, as well as how Overleaf and related tools can help you manage your references.