When a person dies without a will, or dies "intestate" as the law calls it, the property of the deceased is distributed according to a formula fixed by law. In other words, if you do not make a will, you do not have any say about how your property will be distributed. If you make a will, you may name the person that you want to manage the administration of your estate, which is known as the "executor." If you do not make a will, the probate court will appoint someone to handle your estate, which person is known as the "administrator."
Please don't underestimate the importance of a carefully thought out will.