The 476 Visa is only for recent graduates of certain foreign universities. It gives them the chance to get up to 18 months Australian experience in occupations considered in demand. It's not of much use to contractors or freelancers as its a short visa and very specific in terms of who qualifies. You can check whether you qualify on the eligibility calculator here
You can use this visa as a path towards permanent residency of Australia if you have enough points to reach the passmark on teh General Skilled Migration points test.
You can bring secondary applicants with you and both you and they can work or study freely whilst you are in Australia.