What is the difference between a revocable and an irrevocable trust?

A trust created during lifetime (a “living” or “inter vivos” trust) may be revocable, which means it can be revoked or changed by the settlor (the trust creator), or irrevocable, which means it cannot be changed by the settlor. Revocable trusts are commonly used to preserve assets from estate taxes or to avoid probate. Irrevocable trusts are commonly used for asset protection and to preserve assets from nursing home costs.