MyBib is a free online citation bibliography creation tool. It can create citations and bibliographies in many styles such as MLA 7 and 8, APA, Chicago, and more. MyBib allows you to paste in a website URL or even search for a book, article, or other source by title, and will pull most of the information you need to create a citation (though you may need to double check that the information is correct and complete).
Once you've created your citations, MyBib allows you to copy paste your citations, download them as a Word document, save them to your Google Drive, print them, or email them to yourself.
Zotero is, at the most basic level, a reference manager. It is designed to store, manage, and cite bibliographic references, such as books and articles. In Zotero, each of these references constitutes an item. More broadly, Zotero is a powerful tool for collecting and organizing research information and sources.