A formula field is a type of field that calculates a value based on an expression or formula that references other fields or constants. For example, a formula field can display today's date by using the TODAY() function. In this case, the administrator can create a formula field on the account object that updates the audited date field with today's date when the status of the account is changed to 'Audited'. References:
https://help.salesforce.com/s/articleView?id=sf.fields_about_formulas.htm&type=5