You can share references with other users, through group libraries. There are three types of groups on Zotero:
- public groups, with open membership: anyone can view the library and join the group. (here is an example of a public group created by students at the Geneva Graduate Institute)
- public groups, with closed membership: anyone can view the library, but to join the group, you must apply or be invited
- private groups: only members can view the library, and you must be invited to join.
Groups can be created either directly on the Zotero website or by clicking on the New Library button in Zotero 
-> New Group.
Private groups are a good option for students who are working in groups on a project or paper. The person who creates the group becomes the owner of the group and can invite other people to join the group, and decide what rights they have (view, edit). The group uses its storage space from the group owner's account. If the group owner wants to save storage space, he/she can check the "No group file storage" in the group settings, and then the attached files will not be stored on the Zotero website.
Group libraries will appear in a separate section on the left pane of your Zotero library. The items of your group libraries will not appear in your personal library unless you drag and drop them there. And changes you make to a reference in your group library are not be replicated in your personal library.
Participants in a Zotero group can be:
- the owner: the creator of the group becomes the owner. Owners have full control over the group's settings and are the only ones who can change the group type (private, public, open, closed) or delete it. They have all the abilities of admins and cannot leave a group without first making someone else the owner;
- admins: group participants who can manage the group with the owner. They can change group settings, invite members and control access to the library and file storage;
- members can view the group's library, and may have the right to add, edit, and delete library items and attachments.