A will is a written document through which you direct how some or all of your assets will be distributed after your death. Your will also names a personal representative to oversee the probate process. If you have children under the age of 18, a will typically names a guardian who will take care of them and their assets until they reach adulthood. A will may also establish instructions – through testamentary trusts – for the care and distribution of certain assets in favor of beneficiaries. For example, many parents include a simple testamentary trust providing that assets should be held in trust for children and distributed when the child reaches an age at which the child is capable of handling larger sums of money. Trusts can also be an effective means of reducing or eliminating estate taxes, especially for married persons.

A will rarely governs all of a person's assets. Assets transferred to a Revocable Trust during your lifetime (see below) are governed by the Revocable Trust, not your will. Assets owned in joint tenancy pass automatically to the surviving joint tenant upon the death of the other and not under the will of the deceased joint tenant. Certain assets, such as life insurance and retirement accounts, also pass by beneficiary designation and are not governed by a will (see below).