The Zotero Interface
Zotero's interface is composed of three columns moving left to right from general to specific:
(Note: This image is of Zotero after citations have been added. When you first install Zotero your library will be empty.)
The left column is divided into 2 panes:
The upper pane displays your library and any collections or groups you have set up.
- Collections allow you to sort your citations into categories. (See Collections.)
Groups allow you to share a library of citations with multiple people. (See Sharing your Zotero Citations.)
In the lower pane you can browse and sort your citations by tags assigned to them. (See Tags.)
The Actions 
menu in the top-right corner of this column includes import and export functions and the Zotero preferences.