If someone dies without a will, then their estates are divided among their next of kin.
If you were to die without a will and you were survived by a spouse with no children, they would receive your entire estate. If you did have children, two thirds of the estate would belong to your spouse while the final third is distributed evenly among your children.
Should you only be survived by children and no spouse, your estate is equally shared among your offspring.
Your order of kin then goes as follows; parents, siblings, nieces and nephews, any other relative.
Should you not have any living relatives, then your estate will go to the State.
Writing a will can allow you to distribute your estate no matter the status of the order of the kin. It also means that you can include friends in your will.