With group, you can share documents and collaborate. Your professor and your teammates can read what you uploaded and even better they can read your highlights and notes as well.
With the free version, you can create one private or public-invite only group. Each group is limited to 3 members. To create a group, click on "Create Group" from the left pane under Groups. Choose the kind of group you want to create and fill in the necessary information.
Once you have created your group, you can add members and documents to it.
The Overview tab in your group shows the activities going on with the group/group members.
You can like or comment on the posting members made.