For some of our younger posters, knowing what some of these things are would probably be helpful in understanding how helpful they can be to you:
1. A durable general power of attorney (normally regarding financial matters) allows someone you trust to act for you in the event you are unable to make decisions for yourself IF it is what is known as a "springing power". If it is not a springing power, whoever you name can act on your behalf even if you are competent, which is a good thing if you travel frequently (especially overseas), but it does give them the power to do anything you can do normally, so you need to be absolutely sure it's someone you trust completely. A power of attorney terminates at your death and normally doesn't allow the person you appoint to do much more than make funeral arrangements/pay your funeral bill after you die.
2. A power of attorney for health care/health care rep appointment names a person who could make health care decisions for you in the event you are unable to make them yourself.
3. A living will is pretty much a last days document that sets out your feelings about artificial life support issues. As allforfun said, it takes the pressure off of your loved ones.
4. A will sets out what happens to your property when you die, sets out your wishes re: guardians of your children, and names the person or persons you want to handle these matters for you at your death. This person is normally called a personal representative, executor or executrix.
5. A trust is similar to a will in that it sets out what happens to your property at your death, but it can also hold your property while you are living, and can hold assets to be used to care for yourself, your spouse, your children (VERY important thing to think about if you have a special needs child of any age). It it generally a private document and isn't probated of record (made public) at your death.
I'm not a lawyer and this is NOT legal advice. These are just basic descriptions of what these things are in case you want to begin to look into them online or see an attorney about having them prepared. I don't wanna be practicing law without a license or anything. hahaha
This is simply food for thought.