A will, also referred to as a last will and testament, are written instructions to the Probate Court advising how you want your asset and liabilities to be handled and who you want to handle them. A will may also be used to name guardians for any minor or incapacitated 
children, and provide instruction for the creation of a trust so that you may maintain a degree of control over your assets after your death.
Even if you have no minor or incapacitated children, or a revocable living trust, a will is still an essential estate planning document that can be used as a safeguard against the state or Probate Court dictating who handles your affairs or receives your assets in the event your other plans should fail.