It's service

The E-3 classification applies only to nationals of Australia. The beneficiary must be coming to the United States solely to perform services in a specialty occupation. A specialty occupation is one that requires theoretical and practical application of a body of highly specialized knowledge, and attainment of a bachelor’s or higher degree in the specific specialty (or its equivalent) as a minimum for entry into the occupation in the United States.

USCIS does not use the job title, by itself, when determining whether a particular position qualifies as a specialty occupation. USCIS considers the duties of the offered position to evaluate in which occupation the beneficiary will be providing services.

When the duties of the proffered position are in generalized and abstract terms that do not provide sufficient information to assess which occupation the position is in, USCIS issues an RFE (Request for additional Evidence) seeking to establish the Specialty Occupation nature of the position.

An Expert Opinion (Position Evaluation) is treated as additional evidence to address such RFEs. USCIS considers an Expert as a distinguished industry authority in the specific specialty, who has subject matter expertise, active memberships with relevant industry associations and having industry experience working directly in the field of specialty who has exposure to the best practices followed for hiring in the industry. Carnegie Evaluations have retained tenured Professors in over 85 specialties from reputed U.S accredited Universities with active industry associations memberships and relevant industry experience in the specific specialty to provide an opinion on a specific case. An expert opinion focuses on analyzing the detailed position job duties and make the case that, based on the expert’s experience and knowledge of the industry, the duties are consistent with specialty occupation as defined by USCIS. The expert opinion ascertains the industry standard academic prerequisites to fill such a position, the nature & complexity of the specific job duties associated with the position and the suitability of the beneficiary’s qualifications for the position in the relevant occupational fields as outlined in the Occupational Outlook Handbook (OOH) and/or O*Net.