Testate vs. Intestate
If a person left a valid Last Will and Testament when they died, then they have died testate. That Last Will and Testament will contain directions on how their personal property and real property are to be distributed and to whom. If a person dies without leaving a valid Last Will and Testament, then they have died intestate and the probate court with appropriate jurisdiction will determine how that person's personal property and real property will be distributed and to whom according to that State's laws of intestacy. The laws of intestacy are a body of law that determines the distribution of personal propety and real property amongst a person's heirs in an order of priority.
Typically a person's spouse and children are given the highest priority for distribution. If a person dies without a spouse or child, then typically a living parent. If there are no living parents, then the siblings of the deceased are given priority. And this goes on and on, until a living heir with the highest priority is located. Each State may have it's own variation of this body of law, so you should consult with a local attorney to understand how your States prioritizes your heirs.
Thus, it is important that you have an attorney draft your Last Will and Testament according to your wishes, especially if there is someone in your life that you do not want to inherit from your estate. For example, sometimes couples will separate without obtaining a divorce for financial reasons or other personal reasons. That husband or wife may be surprised to learn that his/her children will not inherit from them if they die without a Will because the laws of intestacy in his/her State prioritizes the spouse over the children. Another example is having a child that may have developed a drug problem and you may not want them to inherit a large sum of money. As you know, life circumstances can be messy and complicated. Make sure your concerns and wishes are properly documented and accounted for in a properly executed Last Will and Testament.
It is also important to note that once you sign your Last Will and Testament, you register it with the Registry of Wills and Trusts. If your Will cannot be found at the time of your death, the Court will conclude that you did not have one, and your estate will be distributed according to the laws of intestacy. It is not enough to sign a Will. You must also make sure it can be found!
Below is an example of a prior intestacy chart used in the Commonwealth of Massachusetts to determine the priority of heirs for intestate estates: