Zotero’s Groups feature allows you to share references with other Zotero users. It is a great way to work on collaborative research work. Both Zotero’s sync feature and group feature require you have an account set up on Zotero server.
To create a Zotero group, login to your Zotero account, go to Groups-> Create a New Group. Group has two basic settings:
Your group library will show below your personal library in the left column in Zotero. Items can be dragged into a group from My Library or another group and viewed or edited by other group members. Group libraries are wholly separate from My Library. Any items dragged into them are separate copies and changes to the items will not be reflected in your own copy of the item until you drag it back into My Library.