The majority of shared files for your groups are stored in a dedicated document library on OneDrive for Business, but you can also access additional shared and followed documents that you may need to further collaborate with your group.
A group calendar is a shared calendar where you and every member of your group can schedule and see upcoming events. You can also share the events with other groups in your school or workplace.
Group conversations are stored in the group's mailbox, separated from individual members' mailboxes. The messages in the group inbox are displayed in a list view, which includes members' photos to visually show the contributors to the conversation.
An Office 365 group is a space for team collaboration. It comes with a shared mailbox, calendar, library, OneNote notebook, and planning tool.