What are the differences between living and testamentary trusts?

The principal difference between living and testamentary trusts is when they go into effect.  Living trusts go into legal effect immediately upon signing.  They are known as inter vivos trusts, which means "during lifetime" in Latin.  This distinguishes them from trusts created in wills (testamentary trusts) that do not take legal effect until the maker's death.  Like wills, testamentary trusts go through the probate process and are supervised by the court system, while living trusts escape court supervision.  Living trusts can technically be either revocable or irrevocable, but the term "living trust" commonly refers only to revocable trusts.