From Hosts tab of the Inventory page, you can click the Edit Settings button to change the name or notification settings of a sheet. Superusers can do this for all sheets; otherwise you need to be a sheet owner, or assessment manager or IT staff of the unit that owns the sheet.
Notification settings are used to determine who will receive an email when an assessment survey is launched that includes an asset (host) on that sheet.
Each asset on the sheet has separate entries for Owners, IT Contacts and Users. When an assessment is launched by the assessment manager or superuser, the people who are listed under the categories which have the checkbox checked will be notified. This is a handy way to notify people to log into Isora GRC and answer some questions. (Note that these notification settings look different in the new UI but they work the same way.)
See also: What are notifications?