Daily Digests are a digest of all Reputation Management and Social Marketing notifications from the previous day.
All Business Center users that have permission to an account will automatically be added as notification recipients (SSO partners must manually add recipients). You can manage recipients in the client's Business Profile (the gear icon in the sidebar or from Reputation Management, go to Reports, Edit Report Settings, Manage your daily notification settings).
You can see an example of a Daily Digest email below.
Available Daily and Instant email notification settings.