Lookup Fields
Lookup fields are used when:
- You want to select a record from an existing entity
- When you know that field values can change anytime and are not fixed. For example: Accounts lookup field on Contacts entity
Customer Fields
Customer fields are used when you want to look up to either Accounts or Contacts entity records. For example a Preferred Vendor can either be a person or a company.
You can add these fields to the Form and check the result: