Aw Computing needs to capture a loss reason in rich text field when an opportunity...

Validation rule is a tool that can be used to enforce data quality and business logic by preventing users from saving records that do not meet certain criteria. In this case, a validation rule can be created on the Opportunity object to display an error message if the Stage field is Closed lost and the Loss Reason field is blank. References: https://help.salesforce.com/s/articleView?id=sf.fields_about_validation_rules.htm &type=5