Study and practice of the law is not for those who cannot be bothered with details. Since the beginning of civilization, those who study, write on and practice the law have been people who pay strict attention to the smallest details.
Because today's society so litigious, excruciating attention to detail has become more vital than ever. It is why legal documents tend to be very long and dense, employing highly specialized vocabulary that is often redundant (colloquially known as "Legalese").
The phrase last will and testament is an example. The fact is that "will" and "testament" mean the same thing. It is an example of the frequently redundant phrasing often found in legal documents (the expression cease and desist is another such phrase, often used in restraining orders and injunctions).
The last will and testament is a document that reflects a person's latest wishes regarding the disposal of any assets following his/her death. Technically, it is only the "last" will and testament if the person dies prior to updating it.
It is a good idea to have a will in place throughout one's life, as death waits for no man. This is especially important for those with both considerable assets and potential heirs. Those who die without a will are said to have died intestate. In this situation, the State will determine how the property of the deceased is distributed.
Even if there is a will in place, if the deceased died with unfulfilled obligations - such as outstanding debts - if there is no provision for honoring such obligations (such as a life insurance policy), creditors will have first claim on the deceased's assets, regardless of what is stated in the last will and testament. A person's estate is considered an entity in legal terms, and can be sued in a court of law in the same way as a person or business.