There are many visa options available to people wishing to visit Australia. The appropriate visa will depend, amongst other things, on your purpose for visiting Australia. The most common is the Visitor Visa (subclass 600). Delegates can find out which visa is best for them in the following link: https://immi.homeaffairs.gov.au/visas/getting-a-visa/visa-finder.
Delegates should apply for their visa well in advance of the conference dates. It is strongly recommended that travellers apply at least two months prior to their intended date of departure. The organising committee can provide invitation letters upon request.