There are many types of trusts, and many reasons that people execute them. In its most basic form, a trust is simply an agreement between two people to hold something of value for a period of time under a specific set of instructions. "Will you hold my wallet while I swim in the ocean so it does not get wet. If I drown, please give it to my wife." That was a trust, with me as the grantor, the person holding my wallet as the trustee, and me as the beneficiary. My wife is the substitute beneficiary.