What is it

A trade mark is a type of intellectual property (IP) right which distinguishes your unique brand, product or service from other competitors in the market. A trade mark can be used to protect your business name or aspects of your brand.
Trade marks can be registered or unregistered. A registered trade mark generally provides stronger legal protection than an unregistered trade mark.
Trade marks can be used to protect a logo, phrase, word, letter, colour, sound, smell, picture, movement, aspect of packaging or any combination of these.
You can use the ™ symbol when you want to identify to the market that this is your brand, this is your logo, this is your tag-line to make sure that everyone knows that you are serious about it and are willing to protect it. You can use the ™ symbol on your brand material if you have not filed a trade mark application or you have a pending trade mark but it is not essential and it gives you no legal rights.
Once you have a registered trade mark it is strongly recommended that you mark your brand and any products with the ® symbol. This puts others on notice to respect your trade mark. It is illegal to use the ® symbol before your trade mark is registered. You should only use the ® symbol when you have registered rights in the trade mark. Most businesses will use the ™ symbol all the way up to final registration of their mark and then once it is registered, then change the symbol at the end to ® .
https://progressivelegal.com.au/trade-marks/how-do-i-use-the-tm-or-r-symbol-on-my-trade-mark/#:~:text=You%20can%20use%20the%20%E2%84%A2%20symbol%20on%20your%20brand%20material,gives%20you%20no%20legal%20rights.

Do you need it?

Registering a business name doesn't give you exclusive rights to it. Learn the difference between a business name and trade mark and how you can best protect your brand.

A trade mark can be a letter, number, word, phrase, logo, image, sound, movement, shape or scent. Registering a trade mark gives you exclusive rights to your business name in Australia

If you want exclusive rights to your business name, you'll need to protect it with a trade mark. This will help you:

protect your name and stop others from trading with it
get exclusive use of that trade mark throughout Australia
have protection in all Australian states and territories for an initial period of 10 years.

https://business.gov.au/planning/protect-your-brand-idea-or-creation/difference-between-a-business-name-and-a-trade-mark

So do you need to do it?

No, but it is prudent to do so.

A registered trademark enjoys the protection of the Trade Marks Act 1995 (Cwlth), as well as the protection of the general law.

An unregistered trademark can be protected by the general law only.

https://www.business.qld.gov.au/running-business/risk/ip/ip-kit/browse-ip-topics/names,-such-as-trademarks,-brands,-logos,-domain-names,-business-names-or-company-names/differences#:~:text=A%20trademark%20is%20registered%20to,specific%20type%20of%20legal%20entity.