On a form, which type of field has this icon which can be clicked, to see a preview of the associated record?

"Lookup" is a general term for searching, not a specific field type in ServiceNow that inherently features a preview icon for referenced records.

"Preview" describes the action of viewing, not the name of the specific field type that enables this functionality.

A Reference field is designed to store a link to a record in another table and typically includes a small information icon (e.g., an 'i') which, when clicked, displays a pop-up preview of the referenced record's details without requiring navigation away from the current form.

"Snapshot" is not a recognized ServiceNow field type that provides this specific type of record preview functionality.

"Quickview" is not a standard ServiceNow field type.

"Drilldown" refers to navigating to more detailed data, but not the specific field type or icon associated with previewing a referenced record.