What are the different types of plumbing?

I live in Victoria Australia, and I'm interested in become a plumber, I understand I need to complete a 4 year apprenticeship and the journey man's exam. I just wanted what different forms of plumbing there are and what defines them.

emergency plumber

Plumbers are essential to the installation and maintenance of water systems in various settings, from municipal water supply plants to sewers to commercial and residential facilities. Plumbers frequently specialize in one or more areas of the trade, such as laying water and sewer lines, fitting pipes and valves for pressurized water systems, and performing maintenance on existing fixtures.
Plumbing and heating