In Salesforce, when contacts are created without being associated with an account, they are referred to as
"Private Contacts." Private Contacts are visible only to the record owner and system administrators, and they do not inherit sharing settings from accounts because they aren't linked to any. Since these contacts are not associated with accounts, they remain isolated from standard sharing rules or role hierarchies, emphasizing that only the owner and admin can view them.
For further details, see: Salesforce Private Contacts.