This is called intestacy . If you haven't chosen whom you want to receive your estate, the legislature has tried to guess what you would have done. It's better than nothing. The rules vary from state to state. This description is particularly Illinois.
Somebody is needed to administer the estate.
This is the personal representative. The statute sets out a list of preferences. People who receive under the state's will are called heirs . If there is a spouse and no descendants, it all goes to the spouse. If there are descendants and no spouse, it all goes to the descendants.