Outlook 2016: Office 365 Groups
The new Office Groups option is aimed at teams. You can create your own groups in Outlook 2016, then use those groups across other applications for collaboration. It's like having a project folder accessible to all team members across their Office apps, available from within the email client you likely have open all day anyway. Office Groups already existed in Outlook Web App, but now you can use it in the Outlook 2016 desktop client as well. (Mobile users need to use the separate Office 365 Groups app.)