This is a type of liability insurance (also described in context of tech-covers). It is also known as Professional Indemnity Insurance. As the name suggest, it provides protection to professionals (doctors, lawyers, architects, engineers, advertising firms, etc) for actual or even alleged negligent actions and/or omissions. Not only is there coverage for damage / injury (both physical and non-physical e.g. libel, slander) but also for defense costs incurred which could be substantial.