Contact property priority
When adding new contact properties, you define one or more fields, from which the property gets its value. Priority specifies the order, in which the system checks these fields for value. If the field with priority 1 has no value, the systems checks the field with priority 2 and so on, until there is a field with value. The property gets that value.
For example, there may be several contact fields that mean one and the same thing in your scenario, so you want to use them to fill just one contact property. For example, the Job Title property may come from your CRM system under the name Position, from your website registration form as Job Title, and from several smaller forms on the website as Job. All these fields need to be considered as Job Title but with different priority. The Position field is Priority 1, the Job Title field Priority 2, and finally, if there is no value in these fields, the contact property Job Title uses the data from the Job field from the forms.