A trust is an arrangement which takes effect during the lifetime of the creator of a trust. A trust avoids probate on any assets that are titled in the name of the trust. The terms of the trust must be revealed to the beneficiaries and heirs when the terms become irrevocable. The terms usually become irrevocable when the creator of the trust dies. A trust may also be set up by a Will, which leaves property in trust for a beneficiary. These trusts are called testamentary trusts and are usually irrevocable.