Lookup relationship refers to a relationship between two records so you can associate records with each other. Forexample, cases have a lookup relationship with assets that lets you associate aparticular asset with a case. On one side of the relationship, a lookup field allowsusers to click a lookup icon and select another record from a popup window. On theassociated record, you can then display a related list to show all of the records thathave been linked to it. If a lookup field references a record that has been deleted, bydefault Salesforce clears the lookup field. Alternatively, you can prevent records frombeing deleted if theyre in a lookuprelationship.