Item - a reference or a source of information. Zotero uses "items" to represent references for books, articles, etc.
Library - a master folder of organized references. The default "My Library" is personal and cannot be shared.
Collection - a child folder (sub-folder) found in your Library. You can also have sub-collections within a collection.
Group - a Library used for sharing references with others. There are 3 different types of Group Libraries:
For more information, visit the Zotero documentation topic on groups.
To create a new collection within your Zotero Library, follow these steps:
For more information, visit the Zotero documentation topic on collections.