I often am asked this question, because it is a really important one to understand. Revocable trusts and irrevocable trusts have different purposes, and an estate planning elder law attorney can help you choose the type of trust you should have if you need a trust. Usually the reasons for creating a revocable trust include goals such as avoiding probate, providing privacy, discouraging wills contests, or providing for management of assets. On the other hand, the purpose of an irrevocable trust most often is to provide asset protection or to help a person be in a position in the future to qualify for government help with long term care expenses for which there is no health insurance. This may include planning for Medicaid or for Veterans benefits for Aid and Attendance for a Veteran or Veteran's widow.
It is important to understand that a key difference between a revocable and an irrevocable trust is whether or not it can be changed by the person setting up the trust. When you set up a revocable trust you can change it or terminate it whenever you want (as long as you are competent). When you set up an irrevocable trust, by its nature, it cannot be amended or changed (except in very limited circumstances).
An elder law attorney can help you decide whether you need a trust and, if so, whether it should be revocable or irrevocable based on your particular needs and circumstances.