Employer sponsorship is the process by which an approved Australian employer agrees to support a visa applicant for a work visa. For the Skills in Demand visa (subclass 482), the employer must first be approved as a standard business sponsor before it can nominate anyone.
Once approved as a sponsor, the employer nominates the specific role to be filled. Sponsorship and nomination are separate approvals: being a sponsor establishes the employer's standing, while the nomination ties that standing to a particular job and applicant.