A testamentary trust is one that is not actually effective until after you die. It can be established under your Last Will and Testament, Revocable Living Trust, or Irrevocable Life Insurance Trust. Moreover, all testamentary trusts are irrevocable which means once made, you may not change it. Since a testamentary trust is effective after your death, there is no rational way to change it or to cancel (revoke) it.
A living trust is one that is created, and funded, during one’s lifetime. These are an also known as inter vivos trust, which in Latin means a trust between the living. Living trusts can be revocable (you can terminate it) or irrevocable (once made it cannot be changed or terminated). Whether a living trust is revocable or irrevocable depends on how the trust document is drafted and what its overall purpose is. The assets (corpus) which sit in a living trust are comprised of those assets that are actually transferred into it.