Unfortunately if you pass away without a Will, nobody will know how you wanted your assets divided and who you wanted to entrust the job of carrying out your wishes.
The legal terminology for this situation is “intestacy”. Under the Succession Act 2006 (NSW) what happens is that your assets will be distributed according to a pre-determined order. Certain family members, such as your spouse, will have priority, but for the most part the assets will likely be distributed in a manner which you may not have intended.
Passing away while not having a Will can result in your loved ones going through unnecessary hardship and stress. If you are in a de facto or same sex relationship, your partner will also need to convince the court that the two of you indeed have a relationship.
In addition to this, if the court is unable to determine if you have any relatives or cannot locate any of your relatives, they may end up receiving your estate. While this does not happen often, it is still a possibility.
At the end of the day however, your final wishes really should be documented and made clear for the ones you leave behin.