Zotero's Groups feature allows you to share references with other Zotero users online. It's a great way to work on collaborative research projects.

First, set up Zotero sync and synchronize your library.

• To create a shared library, click the New Group or Feed icon  then select New Group. 
• To join an existing Zotero library, search for it at zotero.org/groups or ask to be invited by the group’s owner.
• You must log in to the zotero.org website to create or join a group.

You now have two sections in your Zotero collections pane: My Library and Group Libraries.

Personal and group libraries are entirely separate, and changes made to items in one library do not affect the other. You can drag items back and forth libraries to copy items.

Search for existing public groups or create a new group. Groups may be public (searchable, and anyone can join) or private (users can only join if invited).