Account Linking means that you can link multiple accounts and view and pay all your open bills with a single transaction. When registering bills under the same email address, you are given the option to link the related accounts within the service.
Multiple first email notifications scheduled for the same day, including for different bill types, are grouped into one email rather than sent separately. Payment receipts are sent individually. Editing account information such as changing an email or password will go across all linked accounts, however, changing settings such as AutoPay or paperless is only for the accessed account.