Zotero and EndNote are 2 different kinds of citation management software. You can use them to collect, organize, and reuse sources that you find in your research. They are especially helpful for creating lists of references in the style you need and for organizing PDFs of articles or reports. You can also share your sources on the web with the web-based versions of EndNote and Zotero.
Zotero is free, and EndNote is free for ASU students, faculty, and staff.