Citations can be arranged according to groups based on user preferences (searches, topics, disciplines, etc.). To create a group, click on Groups in the menu, and then choose "Create Group". Users can then name their respective groups and then click and drag selected citations to the desired group.
Smart Groups are a way to automatically filter citations into particular groups. After clicking "Create Smart Group", select the filter to apply to the citations. Citations will automatically be transferred based on those filters upon import.
The following tutorial outlines the process for creating both types of groups.