Currently Medicare covers a certain amount of a GP visit. I don't know the exact amount, but let's say it's $30. A GP can charge more if they like (unlike the NHS, practices are private businesses, and GPs aren't essentially government employees), and will generally do so, because the Medicare cost hasn't risen at the same rate as the actual cost for the GP. If the cost of a consultation is $40, you'll pay $40 to the receptionist after your consultation, but you'll get a $30 rebate from Medicare (again, because you're dealing with a private business who is being reimbursed by the government). The $10 difference is called the 'gap', and if you're privately insured, the gap may be covered too, in which case you'll end up paying nothing.
However, some GPs 'bulk-bill', which means after your consultation you show your Medicare care and they bill directly to it - but they can then only bill the Medicare amount of $30 (well, 85% of that, which is the trade-off for saving transaction costs). Which means if you're bulk-billed, you'll end up paying nothing, as the entire cost of the consultation is being directly paid for by Medicare. It's up to the GP whether they do this or not, given it limits the fee they can charge, but generally they'll do it for those with lower incomes like pensioners or students, and some GPs run bulk-bill practices, whereby everyone is bulk-billed (though the idea is that the service you're getting won't necessarily be quite as good, and you won't find this in wealthier areas). The changes announced in the federal budget yesterday mean that now if you're bulk-billed you have to make a $6 co-payment. So you'll either have to pay the gap (or pay for insurance which covers it), or pay the $6. Meaning no free consultations. Polls suggest this will deter about 40% of people from visiting a GP.
The changes to student debt are that instead of having it indexed to CPI, it's going to be indexed to some bond measure, which will effectively mean up to 3% extra a year. It seems that this will apply to all currently existing student debt, even though that debt was taken out on the understanding that it'd only be indexed to CPI. If it were a contract rather than a government program, it's be a pretty clear breach.