Can you explain the difference between the post-study work visa and the job seeker visa in Australia?

Australia does not have a separate "job seeker visa."

International graduates typically use the Post-Study Work Visa (Temporary Graduate visa, subclass 485, Post-Study Work stream) to live, work, and look for jobs after completing a degree at an Australian institution. This visa lets you stay temporarily (duration depends on your qualification level) and provides unrestricted work rights. You must apply within six months of finishing your course and meet specific eligibility criteria.

If you want to stay longer after your post-study work visa expires, you must explore other options like skilled migration or employer-sponsored visas.