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.
Having a group conversation is similar to having an e-mail thread but only group members participate. You can start a new conversation with the group members or reply inline to a message. Conversations are stacked in your group inbox, and when you select one, you'll see the original message plus all the replies in sequence from oldest to newest.
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.