Zotero is a free bibliographic management tool that allows you to store and organize your references. You can add references from library databases, add books with websites like Amazon.com and WorldCat.org, and manually add any references, such as websites. You can also insert in-text citations while typing your papers, and generate a bibliography of all your references at the end.
For Zotero for Firefox, click the Zotero icon in the Firefox toolbar to open your Zotero library. This brings up a pane with all of your references, collections, and notes. You can close the Zotero for Firefox pane by clicking on the X icon in the upper right of the Zotero window or by clicking on the toolbar icon again. The Zotero window does not have to be open for you to do “quick saves” of material you want to add to your research collection.
Zotero Standalone can be opened from your operating system's dock or file manager like any other program.