The single biggest thing to understand: in Australia, building the network and selling you internet are done by different companies. NBN / Opticomm build and maintain the infrastructure (fibre, cables, nodes). Your ISP (Telstra, Optus, TPG, Aussie Broadband…) just sells the plan, bills you and does support. In China it's an integrated model — China Telecom/Unicom/Mobile build the network and sell it, so you deal with one company for install, support and repairs. In Australia you're effectively dealing with two layers, even if you only ever talk to your ISP.

• NBN: National Broadband Network — the national infrastructure company (fibre, lines, nodes).
• Opticomm: a private infrastructure company, like a 'building's own broadband', common in newer estates — some new blocks only work with its partner ISPs.
• ISP: Internet Service Provider — the retailer that sells you the plan (Telstra, TPG, etc.).
• RSP: Retail Service Provider — just another name for ISP, emphasising the 'retailer' role.

The split is why support can say ‘it's not our problem.’ If the fault is in the physical line, your ISP has to log it with NBN and wait for an NBN technician — they can't just fix it themselves. It's also why switching ISPs to escape a slow activation often doesn't help: the new ISP still queues behind the same NBN process. And it's why ‘why can't I get provider X at my address?’ comes down to what NBN/Opticomm has physically built there, not the retailer's choice.