The majority of information about a host is contained in the other panels and sections in a Host record (contacts, addresses, industries, tags etc.), but there are some details reserved for the actual Host record that appear at the top left of the screen when you are viewing a host.
These include miscellaneous details such as the Host's actual Name, web site, ABN, status etc.
Typically these details are not updated often after the core record is created, however scenarios where you may have a Host record with just these basic details could be where you are prospecting for new Hosts and have business cards or leads that are entered in Pathways, but yet to be followed up and their records fleshed out with additional detail. This also explains why we have a "Primary Contact" field attached to the host record itself - it's for those "minimum information" scenarios, and often these are the core details available if Pathways is being set up and a basic host list was imported from Excel or some other data source.
TIP: When you create a new host record, the primary contact and phone number you enter to create the host record is used to automatically create the first "Host Contact" record. This is why it's REALLY common to see a Host record with the "Phone 1" on the left being the same as the first Host Contact Phone Number on the right.