Zotero Groups provides a method to collaborate with other Zotero users. There is no limit on how many members may join your group, and your full storage subscription is available to both your personal and group libraries.
To create a new group, click on the "New Library..." icon located next to the New Collection icon in the top left corner of Zotero. When you click on the New Library icon, select "New Group" from the drop-down menu (demonstrated below).
