One day, someone asked me "what would you like for tea?". Then she mentioned roast beef or chicken. I was confused what she meant by tea in this context, and I assumed she was not talking about having a tea with biscuits. Later on, I remembered that tea was actually dinner (too much to remember or too nervous to talk with foreigner ). From that moment, I think learning slang words or expressions is also necessary to avoid misunderstanding or any communication problems.
The following words are Australian slang words and expressions which I have learned before and after I came to Australia.

Aussie/Oz = Australia
Mozzie = mosquito
Maccas = Mcdonalds (fast food resto)
Bogan = people who are uneducated/not smart/not stylish
Footy = football (especially Australian rules)
Barbie = barbeque/bbq
Arvo = afternoon
Tea = dinner
G'day = hello
Joey = baby kangaroo
Mate = buddy, friend
Breakky = breakfast
Thongs = flip-flops
Chips = french fries
Cuppa = cup of tea or coffee
Bottle shop = alcohol shop

Beside words, I also found that people in Australia use different phrases/sentences. Here are some examples:

1. A : Thank you!
B : No worries/no problem (In America, people tend to say "you are
welcome")

2. To offer help
"You right?" = (In America, people would say "may I help you?").

3. Some expressions are usually very brief
- "G'day" instead of "have a good day"
- "See ya/catch ya" instead of "see you later / catch you later"

That's all for now. Hopefully, this thread can be helpful for you and I would be thankful if you can give me