• Exchange Online:
    • Mail (including In-Place Archives also known as Online Archives)
    • Contacts
    • Tasks
    • Calendar
  • OneDrive (not including My Site Host Sites)
  • Groups & Teams
    • Conversations
    • Calendar 
    • Notebook
    • Planner
    • Files 
    • Team Sites
    • Channels
      • Wiki pages
      • Conversations
  • Public Folders
    • All email messages in Public Folders including email messages in sub-folders, but not items that are posted in the Public Folders
    • User Permissions (which are automatically restored together with content)
  • SharePoint
    • Permissions
    • Site Columns
    • Site Content Types
    • Sub-sites
    • Document Libraries of Classic Sites and of Communication Sites
    • Lists
  • SharePoint (Legacy) - formerly called Sites. This is only available for users who had this enabled in versions older than 2.0. This checkbox will eventually be phased out (est. early 2020).
    • Document Libraries of Classic Sites
    • Document Libraries of Communication Sites

For details about SharePoint, see: What SharePoint data can be backed up?

NoteSharePoint, Groups & Teams, and Public Folders are not related to any specific accounts, so if you select any of these, all the data in these areas will be backed up.

To choose what to back up, see: How to configure your backup