A cross object formula field is a type of formula field that references fields from related objects using relationships such as lookup or master-detail. It can be used to display data from one object on another object without creating another relationship or copying data. A cross object formula field can be created on opportunity object to display data from industry field on account object using account ID lookup relationship. A custom account field, a standard account field, or a master-detail relationship field are not types of fields that can display data from industry field on account object on opportunity page layout; they either do not exist or do not reference related objects. References: https://help.salesforce.com/s/articleView?id=sf.cross_object_formulas.htm &type=5