Two different tabs have been added in the Account 360 section. When notes or tasks are added under a contact, it will be also reflected in the Account360 section under task and notes.
If an account has multiple contacts, and a policy or deal is added to that account, it will be available for all the contacts. But if any task or notes is added for any contact under that account, then the task and notes will be available for that specific contact only. And the files will be available for all contacts under that account.