Groups are designed to make it easy to make and share joint events, share publications and files, and make Tasks for other people in the Group. Any collection of people with something in common can form a group, such as Research Groups, Academic/Industrial Collaborations, or Study Groups.
To create a new group:
Navigate to "Groups" from the panel on the left
Select "Create Group"
Set group name, add details, select privacy type
Press "Create Group" on the bottom of the dialog to finish
Note: The different privacy settings are Open (anyone can join), Closed (only invited people can join, but the Group is shown publicly) or Secret (only invited people can join, and the Group is not shown publicly).