PAT testing stands for Portable Appliance Testing. It's used as a method to determine whether or not fixed appliances, consumer electronics & other electrical items in the home & workplace are safe to use.
PAT testing involves a professional completing visual inspections & other tests to check the safety of appliances. They'll then either pass or fail the appliance and provide a certificate.
PAT testing is often used by landlords & employers to ensure that they're carrying out their electrical safety obligations.