If a person passes on without estate planning of any kind, whether that planning is some kind of will or trust, they are said to have died intestate. Intestate law is the law that decides how assets are transferred and creditors satisfied if a person passes on without saying who gets the house, the car or the guarded family apple pie recipe. Intestacy law is a set of fall back provisions or rules that govern where the assets go, so that the state does not have to decide in each individual case what happens. Intestacy laws are like the default settings on computer program; they are there unless you intentionally alter them. Since most people die intestate, state intestacy laws govern how most people's assets are distributed after their' passing. Sometimes, even when a person has a valid will, if that will does not cover some portion of their property, then state intestacy laws will be used as gap-fillers or fallback measures so that all assets are covered.
Although state intestacy laws are best seen as a set of state laws that govern what happens to property left by those who did not make a will or trust, they also reflect some of the other needs a state has. First, states seem to make an attempt to ask what the normal person in the deceased place would want done with their assets. This is an important question because the answers given will reflect what state legislators think a "normal" person is and would want. It is easy for the legislature to over look non-traditional relationships, such as non-marital co-inhabitants, lesbian and gay life partners and children born out of wedlock or even stepchildren. This can bring about tremendous animosity among the people you care most about; so the best plan is to get a will or trust to protect those you love if nothing else.
However, your wishes are not the only goal that states keep in mind in drafting intestacy laws. The state may wish to maintain a system where parcels of land are owned by a single person rather than a group of people; because such groups have a tendency to sue each other over property they all have an interest in and this creates problems and expenses for the state itself. In addition, your state may have an avowed policy of attempting to promote "traditional family" relationships and use its power to craft intestacy laws to give assets to family members that the state deems more worthy. Even if you are someone who normally prefers more traditional family relationships, there is no guarantee that the relationships your state decides are traditional and your understanding of the traditional family will be the same.
Finally, you are in the best position to decide who is to have your assets, because you actually know the people involved; to the state the people involved are people who occupy abstract positions in your life, like spouse, child or parent. You are the one who is in the best position to decide who among your heirs should get something (or anything at all) from your estate, because these people play a greater role in your life than merely occupying some abstract position. They are the people you have laughed with, shared meals with, raised and have had raise you, cuddled with and loved. This is by no means to suggest that what people mean to you can only be known through your will or even be known through your will at all. It is rather to suggest that you should decide who gets what asset because you know what those around you value and enjoy. You should decide what happens with your assets, because chances are you earned them and should be the one to decide how they would best be passed on.