A will is a legal document in which you give specific instructions to be carried out after your death.  A will can do a variety of things: give instructions as to your funeral arrangements; assign an executor to administer your estate; assign beneficiaries for your assets; divide your assets; etc.  In California, a will is valid if: 1) you are 18 years of age; 2) you were of sound mind when creating your will; 3) you signed your will; and 4) you had two witnesses present at the time you signed your will who acknowledge with their signatures that you knew you were signing your will.