Why is Australia split into 5 parts?

What I Already Know:

- There are five states.

- The Europeans discovered Australia by a portuguese expedition.

 - It was discovered in 1521.

 - Western Australia is the biggest part.

 - there was a tribe named the aboriginals that lived there when they discovered it.

 - they had to fight for survival and survive during harsh dry seasons.

-  It is an island.

- It is split into 5 parts

My questions:

- What are these “parts” called?

- Why are they so big?

- How did they name them?

- Who decided to split this country?

- Who did this?

- How did this happen?

- Is it because a historical feature that slowly split them?

- Was it because of a war?

- When did this happen?

- Why did it happen?

- When was this discovered?

The Facts I Found Out

By computer:

- The “ Parts” of Australia are Northern Australia, Western Australia, Queensland, New South Wales, South Australia, Northern Territory.

-  The biggest “ part” is Western Australia.

- Australia borders the Indian Ocean and the North Pacific Ocean.

- Australia is landlocked.

- Western Australia is the capital ‘part’