A workflow rule with three field updates is a way of setting up automation to update three fields on the Shipment custom object in a very specific order. A workflow rule is a rule that triggers one or more actions when a record meets certain criteria. A field update is an action that updates the value of a field on a record. In this case, you can create a workflow rule that evaluates the Shipment records when they are created or edited, and specify the criteria for triggering the rule. Then, you can add three field updates as the actions for the rule, and enter them in the correct order. The order of the field updates determines the order of execution, and you can change it by using the arrows on the workflow page. References:
https://help.salesforce.com/s/articleView?id=sf.workflow_rules.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.workflow_field_update_considerations.htm&type=5