Who can make a will?

Who can make a will?
Who can make out a will? A Living Will? Or a Durable Power of Attorney? What are the differences between these 3? What are the benefits of having any of these 3? When should these 3 be used?
I am writing a research paper for school, and I chose the topic, ”Why It’s Important to Prepare a Will, Living Will, and/or Durable Power of Attorney.”
Please help me out if you can.
Sincerely,
A Northwestern Business College student

Brother buffalowed me My father died almost 5 years ago with no will.

Brother buffalowed me
My father died almost 5 years ago with no will. My mother never did anything about changing any of the bills from his name to hers, nor did she inform the bank that he died, so both of their names remained on the checking account and the equity line of credit on the house (its only encumberance). A few months ago my mom passed away, also without a will. I have been living in their house for several years taking care of both of them, thus have had no other employment. My brother wants to buy the house and move into it. Since I have no income my brother paid a paralegal to draw up an agreement between him and me wherein I allow him to buy me out of the house (the only asset) at less than half its appraised value and then in addition a quit claim deed for me to sign. The terms were not exactly what we discussed but I felt very pressured (he has all the power here) and signed everything anyway. The quit claim deed was notarized, the agreement was not. Now I realize that I have been royally screwed and want to know if there is anything I can do about it. Is what my brother did legal? How can he have me sign a quit claim deed to a property that isn’t even in my name? Doesn’t this all need to go through probate?